diff --git a/data/schemas/com.project200.data.local.UndabangDatabase/2.json b/data/schemas/com.project200.data.local.UndabangDatabase/2.json
new file mode 100644
index 00000000..b31fddfa
--- /dev/null
+++ b/data/schemas/com.project200.data.local.UndabangDatabase/2.json
@@ -0,0 +1,395 @@
+{
+  "formatVersion": 1,
+  "database": {
+    "version": 2,
+    "identityHash": "cc3993046ab06f37e7ded4f707201ced",
+    "entities": [
+      {
+        "tableName": "exercise_count",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`memberId` TEXT NOT NULL, `date` TEXT NOT NULL, `count` INTEGER NOT NULL, PRIMARY KEY(`memberId`, `date`))",
+        "fields": [
+          {
+            "fieldPath": "memberId",
+            "columnName": "memberId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "date",
+            "columnName": "date",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "count",
+            "columnName": "count",
+            "affinity": "INTEGER",
+            "notNull": true
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": false,
+          "columnNames": [
+            "memberId",
+            "date"
+          ]
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "exercise_list_item",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`memberId` TEXT NOT NULL, `localId` TEXT NOT NULL, `serverId` INTEGER, `syncState` TEXT NOT NULL, `date` TEXT NOT NULL, `sortOrder` INTEGER NOT NULL, `title` TEXT NOT NULL, `personalType` TEXT NOT NULL, `startedAt` TEXT NOT NULL, `endedAt` TEXT NOT NULL, `thumbnailUrls` TEXT, PRIMARY KEY(`memberId`, `localId`))",
+        "fields": [
+          {
+            "fieldPath": "memberId",
+            "columnName": "memberId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "localId",
+            "columnName": "localId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "serverId",
+            "columnName": "serverId",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "syncState",
+            "columnName": "syncState",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "date",
+            "columnName": "date",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "sortOrder",
+            "columnName": "sortOrder",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "title",
+            "columnName": "title",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "personalType",
+            "columnName": "personalType",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "startedAt",
+            "columnName": "startedAt",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "endedAt",
+            "columnName": "endedAt",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "thumbnailUrls",
+            "columnName": "thumbnailUrls",
+            "affinity": "TEXT",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": false,
+          "columnNames": [
+            "memberId",
+            "localId"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_exercise_list_item_memberId_date",
+            "unique": false,
+            "columnNames": [
+              "memberId",
+              "date"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_exercise_list_item_memberId_date` ON `${TABLE_NAME}` (`memberId`, `date`)"
+          },
+          {
+            "name": "index_exercise_list_item_memberId_serverId",
+            "unique": false,
+            "columnNames": [
+              "memberId",
+              "serverId"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_exercise_list_item_memberId_serverId` ON `${TABLE_NAME}` (`memberId`, `serverId`)"
+          }
+        ],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "exercise_record_detail",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`memberId` TEXT NOT NULL, `localId` TEXT NOT NULL, `serverId` INTEGER, `syncState` TEXT NOT NULL, `title` TEXT NOT NULL, `detail` TEXT NOT NULL, `personalType` TEXT NOT NULL, `startedAt` TEXT NOT NULL, `endedAt` TEXT NOT NULL, `location` TEXT NOT NULL, `pictures` TEXT, PRIMARY KEY(`memberId`, `localId`))",
+        "fields": [
+          {
+            "fieldPath": "memberId",
+            "columnName": "memberId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "localId",
+            "columnName": "localId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "serverId",
+            "columnName": "serverId",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "syncState",
+            "columnName": "syncState",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "title",
+            "columnName": "title",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "detail",
+            "columnName": "detail",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "personalType",
+            "columnName": "personalType",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "startedAt",
+            "columnName": "startedAt",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "endedAt",
+            "columnName": "endedAt",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "location",
+            "columnName": "location",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "pictures",
+            "columnName": "pictures",
+            "affinity": "TEXT",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": false,
+          "columnNames": [
+            "memberId",
+            "localId"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_exercise_record_detail_memberId_serverId",
+            "unique": false,
+            "columnNames": [
+              "memberId",
+              "serverId"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_exercise_record_detail_memberId_serverId` ON `${TABLE_NAME}` (`memberId`, `serverId`)"
+          }
+        ],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "simple_timer",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`memberId` TEXT NOT NULL, `localId` TEXT NOT NULL, `serverId` INTEGER, `syncState` TEXT NOT NULL, `time` INTEGER NOT NULL, `createRequestId` TEXT NOT NULL, `pendingEditId` TEXT, `editedAt` INTEGER NOT NULL, PRIMARY KEY(`memberId`, `localId`))",
+        "fields": [
+          {
+            "fieldPath": "memberId",
+            "columnName": "memberId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "localId",
+            "columnName": "localId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "serverId",
+            "columnName": "serverId",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "syncState",
+            "columnName": "syncState",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "time",
+            "columnName": "time",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "createRequestId",
+            "columnName": "createRequestId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "pendingEditId",
+            "columnName": "pendingEditId",
+            "affinity": "TEXT",
+            "notNull": false
+          },
+          {
+            "fieldPath": "editedAt",
+            "columnName": "editedAt",
+            "affinity": "INTEGER",
+            "notNull": true
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": false,
+          "columnNames": [
+            "memberId",
+            "localId"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_simple_timer_memberId_serverId",
+            "unique": false,
+            "columnNames": [
+              "memberId",
+              "serverId"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_simple_timer_memberId_serverId` ON `${TABLE_NAME}` (`memberId`, `serverId`)"
+          }
+        ],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "custom_timer",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`memberId` TEXT NOT NULL, `localId` TEXT NOT NULL, `serverId` INTEGER, `syncState` TEXT NOT NULL, `name` TEXT NOT NULL, `steps` TEXT NOT NULL, `createRequestId` TEXT NOT NULL, `pendingEditId` TEXT, `editedAt` INTEGER NOT NULL, PRIMARY KEY(`memberId`, `localId`))",
+        "fields": [
+          {
+            "fieldPath": "memberId",
+            "columnName": "memberId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "localId",
+            "columnName": "localId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "serverId",
+            "columnName": "serverId",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "syncState",
+            "columnName": "syncState",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "name",
+            "columnName": "name",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "steps",
+            "columnName": "steps",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "createRequestId",
+            "columnName": "createRequestId",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "pendingEditId",
+            "columnName": "pendingEditId",
+            "affinity": "TEXT",
+            "notNull": false
+          },
+          {
+            "fieldPath": "editedAt",
+            "columnName": "editedAt",
+            "affinity": "INTEGER",
+            "notNull": true
+          }
+        ],
+        "primaryKey": {
+          "autoGenerate": false,
+          "columnNames": [
+            "memberId",
+            "localId"
+          ]
+        },
+        "indices": [
+          {
+            "name": "index_custom_timer_memberId_serverId",
+            "unique": false,
+            "columnNames": [
+              "memberId",
+              "serverId"
+            ],
+            "orders": [],
+            "createSql": "CREATE INDEX IF NOT EXISTS `index_custom_timer_memberId_serverId` ON `${TABLE_NAME}` (`memberId`, `serverId`)"
+          }
+        ],
+        "foreignKeys": []
+      }
+    ],
+    "views": [],
+    "setupQueries": [
+      "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)",
+      "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, 'cc3993046ab06f37e7ded4f707201ced')"
+    ]
+  }
+}
\ No newline at end of file
diff --git a/data/src/main/java/com/project200/data/datasource/TimerLocalDataSource.kt b/data/src/main/java/com/project200/data/datasource/TimerLocalDataSource.kt
new file mode 100644
index 00000000..87c3c23b
--- /dev/null
+++ b/data/src/main/java/com/project200/data/datasource/TimerLocalDataSource.kt
@@ -0,0 +1,179 @@
+package com.project200.data.datasource
+
+import com.project200.data.local.PreferenceManager
+import com.project200.data.local.dao.TimerDao
+import com.project200.data.local.entity.CachedTimerStep
+import com.project200.data.local.entity.CustomTimerEntity
+import com.project200.data.local.entity.SimpleTimerEntity
+import com.project200.data.local.entity.SyncState
+import timber.log.Timber
+import java.util.UUID
+import javax.inject.Inject
+
+/**
+ * 타이머를 읽고 씁니다. 기기가 원본이라 서버 응답 없이도 생성과 수정이 끝납니다.
+ *
+ * 계정 조건을 여기서 한 번에 겁니다. 호출부가 memberId를 넘기지 않게 해서 조건을
+ * 빠뜨린 쿼리가 나올 자리를 없앱니다
+ *
+ * 상태 전이 규칙은 셋입니다.
+ * 생성 대기 행을 고치면 생성 대기를 유지합니다. 수정 대기로 바꾸면 전송 작업이
+ * 서버에 없는 항목에 수정 요청을 보냅니다
+ * 생성 대기 행을 지우면 서버가 모르는 행이라 즉시 지웁니다
+ * 서버에 있는 행을 지우면 삭제 대기로 표시만 합니다. 바로 지우면 서버에 알릴 방법이 없습니다
+ */
+class TimerLocalDataSource
+    @Inject
+    constructor(
+        private val timerDao: TimerDao,
+        private val preferenceManager: PreferenceManager,
+    ) {
+        suspend fun getSimpleTimers(): List<SimpleTimerEntity> {
+            val memberId = currentMemberId() ?: return emptyList()
+            return timerDao.getSimpleTimers(memberId)
+        }
+
+        suspend fun countSimpleTimers(): Int {
+            val memberId = currentMemberId() ?: return 0
+            return timerDao.countSimpleTimers(memberId)
+        }
+
+        suspend fun createSimpleTimer(time: Int): String? {
+            val memberId = currentMemberId() ?: return null
+            val localId = newId()
+            timerDao.upsertSimpleTimer(
+                SimpleTimerEntity(
+                    memberId = memberId,
+                    localId = localId,
+                    serverId = null,
+                    syncState = SyncState.CREATE_PENDING,
+                    time = time,
+                    createRequestId = newId(),
+                    pendingEditId = null,
+                    editedAt = now(),
+                ),
+            )
+            return localId
+        }
+
+        suspend fun updateSimpleTimer(
+            localId: String,
+            time: Int,
+        ) {
+            val memberId = currentMemberId() ?: return
+            val current = timerDao.getSimpleTimer(memberId, localId) ?: return
+            timerDao.upsertSimpleTimer(
+                current.copy(
+                    time = time,
+                    syncState = nextStateOnEdit(current.syncState),
+                    pendingEditId = newId(),
+                    editedAt = now(),
+                ),
+            )
+        }
+
+        suspend fun deleteSimpleTimer(localId: String) {
+            val memberId = currentMemberId() ?: return
+            val current = timerDao.getSimpleTimer(memberId, localId) ?: return
+            if (current.serverId == null) {
+                timerDao.deleteSimpleTimer(memberId, localId)
+                return
+            }
+            timerDao.upsertSimpleTimer(
+                current.copy(
+                    syncState = SyncState.DELETE_PENDING,
+                    pendingEditId = newId(),
+                    editedAt = now(),
+                ),
+            )
+        }
+
+        suspend fun getCustomTimers(): List<CustomTimerEntity> {
+            val memberId = currentMemberId() ?: return emptyList()
+            return timerDao.getCustomTimers(memberId)
+        }
+
+        suspend fun getCustomTimer(localId: String): CustomTimerEntity? {
+            val memberId = currentMemberId() ?: return null
+            return timerDao.getCustomTimer(memberId, localId)
+        }
+
+        suspend fun createCustomTimer(
+            name: String,
+            steps: List<CachedTimerStep>,
+        ): String? {
+            val memberId = currentMemberId() ?: return null
+            val localId = newId()
+            timerDao.upsertCustomTimer(
+                CustomTimerEntity(
+                    memberId = memberId,
+                    localId = localId,
+                    serverId = null,
+                    syncState = SyncState.CREATE_PENDING,
+                    name = name,
+                    steps = steps,
+                    createRequestId = newId(),
+                    pendingEditId = null,
+                    editedAt = now(),
+                ),
+            )
+            return localId
+        }
+
+        suspend fun updateCustomTimer(
+            localId: String,
+            name: String,
+            steps: List<CachedTimerStep>,
+        ) {
+            val memberId = currentMemberId() ?: return
+            val current = timerDao.getCustomTimer(memberId, localId) ?: return
+            timerDao.upsertCustomTimer(
+                current.copy(
+                    name = name,
+                    steps = steps,
+                    syncState = nextStateOnEdit(current.syncState),
+                    pendingEditId = newId(),
+                    editedAt = now(),
+                ),
+            )
+        }
+
+        suspend fun deleteCustomTimer(localId: String) {
+            val memberId = currentMemberId() ?: return
+            val current = timerDao.getCustomTimer(memberId, localId) ?: return
+            if (current.serverId == null) {
+                timerDao.deleteCustomTimer(memberId, localId)
+                return
+            }
+            timerDao.upsertCustomTimer(
+                current.copy(
+                    syncState = SyncState.DELETE_PENDING,
+                    pendingEditId = newId(),
+                    editedAt = now(),
+                ),
+            )
+        }
+
+        suspend fun getPendingSimpleTimers(): List<SimpleTimerEntity> {
+            val memberId = currentMemberId() ?: return emptyList()
+            return timerDao.getPendingSimpleTimers(memberId)
+        }
+
+        suspend fun getPendingCustomTimers(): List<CustomTimerEntity> {
+            val memberId = currentMemberId() ?: return emptyList()
+            return timerDao.getPendingCustomTimers(memberId)
+        }
+
+        private fun nextStateOnEdit(current: SyncState): SyncState =
+            if (current == SyncState.CREATE_PENDING) SyncState.CREATE_PENDING else SyncState.UPDATE_PENDING
+
+        private fun newId(): String = UUID.randomUUID().toString()
+
+        private fun now(): Long = System.currentTimeMillis()
+
+        private fun currentMemberId(): String? {
+            return preferenceManager.getMemberId().also {
+                if (it == null) Timber.w("회원ID가 없어 타이머 저장을 건너뜁니다")
+            }
+        }
+    }
diff --git a/data/src/main/java/com/project200/data/di/DatabaseModule.kt b/data/src/main/java/com/project200/data/di/DatabaseModule.kt
index 44739e85..8c80dce7 100644
--- a/data/src/main/java/com/project200/data/di/DatabaseModule.kt
+++ b/data/src/main/java/com/project200/data/di/DatabaseModule.kt
@@ -7,6 +7,7 @@ import com.project200.data.local.UndabangDatabase
 import com.project200.data.local.UndabangTypeConverters
 import com.project200.data.local.dao.ExerciseCountDao
 import com.project200.data.local.dao.ExerciseRecordDao
+import com.project200.data.local.dao.TimerDao
 import com.project200.domain.manager.SessionDataCleaner
 import com.squareup.moshi.Moshi
 import dagger.Binds
@@ -67,5 +68,11 @@ abstract class DatabaseModule {
         fun provideExerciseRecordDao(database: UndabangDatabase): ExerciseRecordDao {
             return database.exerciseRecordDao()
         }
+
+        @Provides
+        @Singleton
+        fun provideTimerDao(database: UndabangDatabase): TimerDao {
+            return database.timerDao()
+        }
     }
 }
diff --git a/data/src/main/java/com/project200/data/impl/TimerRepositoryImpl.kt b/data/src/main/java/com/project200/data/impl/TimerRepositoryImpl.kt
index 446a8775..55269fb5 100644
--- a/data/src/main/java/com/project200/data/impl/TimerRepositoryImpl.kt
+++ b/data/src/main/java/com/project200/data/impl/TimerRepositoryImpl.kt
@@ -51,7 +51,10 @@ class TimerRepositoryImpl
             return apiCallBuilder(
                 ioDispatcher = ioDispatcher,
                 apiCall = { apiService.postSimpleTimer(SimpleTimerRequest(time)) },
-                mapper = { dto: SimpleTimerIdDTO? -> dto?.simpleTimerId ?: -1L },
+                // 서버 ID 없이 성공으로 올리면 로컬이 원본이 될 때 복구 못 하는 행이 생깁니다
+                mapper = { dto: SimpleTimerIdDTO? ->
+                    dto?.simpleTimerId ?: throw IllegalStateException("simpleTimerId가 없습니다")
+                },
             )
         }
 
@@ -80,7 +83,7 @@ class TimerRepositoryImpl
                 ioDispatcher = ioDispatcher,
                 apiCall = { apiService.getCustomTimer(customTimerId) },
                 mapper = { dto: GetCustomTimerDetailDTO? ->
-                    dto?.toModel() ?: CustomTimer(-1L, "")
+                    (dto ?: throw IllegalStateException("커스텀 타이머 상세가 없습니다")).toModel()
                 },
             )
         }
diff --git a/data/src/main/java/com/project200/data/local/UndabangDatabase.kt b/data/src/main/java/com/project200/data/local/UndabangDatabase.kt
index c701526f..5a81bf25 100644
--- a/data/src/main/java/com/project200/data/local/UndabangDatabase.kt
+++ b/data/src/main/java/com/project200/data/local/UndabangDatabase.kt
@@ -5,9 +5,12 @@ import androidx.room.RoomDatabase
 import androidx.room.TypeConverters
 import com.project200.data.local.dao.ExerciseCountDao
 import com.project200.data.local.dao.ExerciseRecordDao
+import com.project200.data.local.dao.TimerDao
+import com.project200.data.local.entity.CustomTimerEntity
 import com.project200.data.local.entity.ExerciseCountEntity
 import com.project200.data.local.entity.ExerciseListItemEntity
 import com.project200.data.local.entity.ExerciseRecordDetailEntity
+import com.project200.data.local.entity.SimpleTimerEntity
 
 /**
  * 오프라인 캐시용 로컬 데이터베이스입니다.
@@ -20,8 +23,10 @@ import com.project200.data.local.entity.ExerciseRecordDetailEntity
         ExerciseCountEntity::class,
         ExerciseListItemEntity::class,
         ExerciseRecordDetailEntity::class,
+        SimpleTimerEntity::class,
+        CustomTimerEntity::class,
     ],
-    version = 1,
+    version = 2,
     exportSchema = true,
 )
 @TypeConverters(UndabangTypeConverters::class)
@@ -30,6 +35,8 @@ abstract class UndabangDatabase : RoomDatabase() {
 
     abstract fun exerciseRecordDao(): ExerciseRecordDao
 
+    abstract fun timerDao(): TimerDao
+
     companion object {
         const val DATABASE_NAME = "undabang.db"
     }
diff --git a/data/src/main/java/com/project200/data/local/UndabangTypeConverters.kt b/data/src/main/java/com/project200/data/local/UndabangTypeConverters.kt
index 56c32b90..6ba213a1 100644
--- a/data/src/main/java/com/project200/data/local/UndabangTypeConverters.kt
+++ b/data/src/main/java/com/project200/data/local/UndabangTypeConverters.kt
@@ -3,6 +3,7 @@ package com.project200.data.local
 import androidx.room.ProvidedTypeConverter
 import androidx.room.TypeConverter
 import com.project200.data.local.entity.CachedPicture
+import com.project200.data.local.entity.CachedTimerStep
 import com.project200.data.local.entity.SyncState
 import com.squareup.moshi.Moshi
 import com.squareup.moshi.Types
@@ -30,6 +31,11 @@ class UndabangTypeConverters(moshi: Moshi) {
             Types.newParameterizedType(List::class.java, CachedPicture::class.java),
         )
 
+    private val timerStepListAdapter =
+        moshi.adapter<List<CachedTimerStep>>(
+            Types.newParameterizedType(List::class.java, CachedTimerStep::class.java),
+        )
+
     @TypeConverter
     fun fromSyncState(value: SyncState?): String? = value?.name
 
@@ -59,4 +65,10 @@ class UndabangTypeConverters(moshi: Moshi) {
 
     @TypeConverter
     fun toPictureList(value: String?): List<CachedPicture>? = value?.let(pictureListAdapter::fromJson)
+
+    @TypeConverter
+    fun fromTimerStepList(value: List<CachedTimerStep>?): String? = value?.let(timerStepListAdapter::toJson)
+
+    @TypeConverter
+    fun toTimerStepList(value: String?): List<CachedTimerStep>? = value?.let(timerStepListAdapter::fromJson)
 }
diff --git a/data/src/main/java/com/project200/data/local/dao/TimerDao.kt b/data/src/main/java/com/project200/data/local/dao/TimerDao.kt
new file mode 100644
index 00000000..29d3f900
--- /dev/null
+++ b/data/src/main/java/com/project200/data/local/dao/TimerDao.kt
@@ -0,0 +1,93 @@
+package com.project200.data.local.dao
+
+import androidx.room.Dao
+import androidx.room.Query
+import androidx.room.Upsert
+import com.project200.data.local.entity.CustomTimerEntity
+import com.project200.data.local.entity.SimpleTimerEntity
+import com.project200.data.local.entity.SyncState
+
+@Dao
+interface TimerDao {
+    /** 삭제 대기 행은 화면에서 이미 사라진 타이머라 조회에서 뺍니다 */
+    @Query(
+        "SELECT * FROM simple_timer " +
+            "WHERE memberId = :memberId AND syncState != :excluded " +
+            "ORDER BY time",
+    )
+    suspend fun getSimpleTimers(
+        memberId: String,
+        excluded: SyncState = SyncState.DELETE_PENDING,
+    ): List<SimpleTimerEntity>
+
+    /** 최대 6개 제한을 로컬에서 판정할 때 씁니다 */
+    @Query(
+        "SELECT COUNT(*) FROM simple_timer " +
+            "WHERE memberId = :memberId AND syncState != :excluded",
+    )
+    suspend fun countSimpleTimers(
+        memberId: String,
+        excluded: SyncState = SyncState.DELETE_PENDING,
+    ): Int
+
+    @Query("SELECT * FROM simple_timer WHERE memberId = :memberId AND localId = :localId")
+    suspend fun getSimpleTimer(
+        memberId: String,
+        localId: String,
+    ): SimpleTimerEntity?
+
+    @Upsert
+    suspend fun upsertSimpleTimer(timer: SimpleTimerEntity)
+
+    @Query("DELETE FROM simple_timer WHERE memberId = :memberId AND localId = :localId")
+    suspend fun deleteSimpleTimer(
+        memberId: String,
+        localId: String,
+    )
+
+    @Query(
+        "SELECT * FROM custom_timer " +
+            "WHERE memberId = :memberId AND syncState != :excluded " +
+            "ORDER BY editedAt",
+    )
+    suspend fun getCustomTimers(
+        memberId: String,
+        excluded: SyncState = SyncState.DELETE_PENDING,
+    ): List<CustomTimerEntity>
+
+    @Query("SELECT * FROM custom_timer WHERE memberId = :memberId AND localId = :localId")
+    suspend fun getCustomTimer(
+        memberId: String,
+        localId: String,
+    ): CustomTimerEntity?
+
+    @Upsert
+    suspend fun upsertCustomTimer(timer: CustomTimerEntity)
+
+    @Query("DELETE FROM custom_timer WHERE memberId = :memberId AND localId = :localId")
+    suspend fun deleteCustomTimer(
+        memberId: String,
+        localId: String,
+    )
+
+    /** 전송할 대기 행입니다. 워커가 씁니다 */
+    @Query(
+        "SELECT * FROM simple_timer " +
+            "WHERE memberId = :memberId AND syncState != :synced " +
+            "ORDER BY editedAt",
+    )
+    suspend fun getPendingSimpleTimers(
+        memberId: String,
+        synced: SyncState = SyncState.SYNCED,
+    ): List<SimpleTimerEntity>
+
+    @Query(
+        "SELECT * FROM custom_timer " +
+            "WHERE memberId = :memberId AND syncState != :synced " +
+            "ORDER BY editedAt",
+    )
+    suspend fun getPendingCustomTimers(
+        memberId: String,
+        synced: SyncState = SyncState.SYNCED,
+    ): List<CustomTimerEntity>
+}
diff --git a/data/src/main/java/com/project200/data/local/entity/CachedTimerStep.kt b/data/src/main/java/com/project200/data/local/entity/CachedTimerStep.kt
new file mode 100644
index 00000000..ed1e2364
--- /dev/null
+++ b/data/src/main/java/com/project200/data/local/entity/CachedTimerStep.kt
@@ -0,0 +1,16 @@
+package com.project200.data.local.entity
+
+import com.squareup.moshi.JsonClass
+
+/**
+ * 커스텀 타이머의 스텝 한 줄입니다.
+ *
+ * 서버 스텝 ID를 담지 않습니다. 서버 수정이 전체 교체(PUT)라서 스텝 ID가 왕복에서
+ * 유지된다는 보장이 없습니다
+ */
+@JsonClass(generateAdapter = true)
+data class CachedTimerStep(
+    val order: Int,
+    val name: String,
+    val time: Int,
+)
diff --git a/data/src/main/java/com/project200/data/local/entity/CustomTimerEntity.kt b/data/src/main/java/com/project200/data/local/entity/CustomTimerEntity.kt
new file mode 100644
index 00000000..44e51cd3
--- /dev/null
+++ b/data/src/main/java/com/project200/data/local/entity/CustomTimerEntity.kt
@@ -0,0 +1,30 @@
+package com.project200.data.local.entity
+
+import androidx.room.Entity
+import androidx.room.Index
+
+/**
+ * 커스텀 타이머입니다. 기기가 원본입니다.
+ *
+ * 이름과 스텝 목록을 묶어 타이머 하나가 판정 단위입니다. 스텝만 따로 조회할 일이 없고
+ * 서버 수정도 전체 교체라서 스텝을 JSON 컬럼에 담습니다
+ *
+ * 목록 정렬은 editedAt으로 합니다. 서버 응답 순서를 그대로 보존해야 하면
+ * 서버 목록 반영을 붙이는 이슈에서 순서 컬럼을 추가합니다
+ */
+@Entity(
+    tableName = "custom_timer",
+    primaryKeys = ["memberId", "localId"],
+    indices = [Index(value = ["memberId", "serverId"])],
+)
+data class CustomTimerEntity(
+    val memberId: String,
+    val localId: String,
+    val serverId: Long?,
+    val syncState: SyncState,
+    val name: String,
+    val steps: List<CachedTimerStep>,
+    val createRequestId: String,
+    val pendingEditId: String?,
+    val editedAt: Long,
+)
diff --git a/data/src/main/java/com/project200/data/local/entity/SimpleTimerEntity.kt b/data/src/main/java/com/project200/data/local/entity/SimpleTimerEntity.kt
new file mode 100644
index 00000000..aa91e33c
--- /dev/null
+++ b/data/src/main/java/com/project200/data/local/entity/SimpleTimerEntity.kt
@@ -0,0 +1,32 @@
+package com.project200.data.local.entity
+
+import androidx.room.Entity
+import androidx.room.Index
+
+/**
+ * 심플 타이머입니다. 기기가 원본입니다.
+ *
+ * 행을 식별하는 값은 localId입니다. 오프라인에서 만든 타이머는 서버 ID를 받기 전이라
+ * serverId가 비어 있습니다
+ *
+ * 목록 정렬은 화면이 시간 오름차순과 내림차순을 토글하므로 여기서는 정하지 않습니다
+ *
+ * @property createRequestId 생성 요청 식별자. 재시도에도 같은 값을 보내 중복 생성을 막습니다
+ * @property pendingEditId 수정과 삭제 요청 식별자. 저장할 때마다 새로 발급합니다
+ * @property editedAt 기기가 저장 시점에 찍은 편집 시각(epoch millis). 충돌 판정 기준입니다
+ */
+@Entity(
+    tableName = "simple_timer",
+    primaryKeys = ["memberId", "localId"],
+    indices = [Index(value = ["memberId", "serverId"])],
+)
+data class SimpleTimerEntity(
+    val memberId: String,
+    val localId: String,
+    val serverId: Long?,
+    val syncState: SyncState,
+    val time: Int,
+    val createRequestId: String,
+    val pendingEditId: String?,
+    val editedAt: Long,
+)
diff --git a/data/src/test/java/com/project200/data/datasource/TimerLocalDataSourceTest.kt b/data/src/test/java/com/project200/data/datasource/TimerLocalDataSourceTest.kt
new file mode 100644
index 00000000..983328f2
--- /dev/null
+++ b/data/src/test/java/com/project200/data/datasource/TimerLocalDataSourceTest.kt
@@ -0,0 +1,238 @@
+package com.project200.data.datasource
+
+import com.google.common.truth.Truth.assertThat
+import com.project200.data.local.PreferenceManager
+import com.project200.data.local.UndabangDatabase
+import com.project200.data.local.createInMemoryDatabase
+import com.project200.data.local.entity.CachedTimerStep
+import com.project200.data.local.entity.SyncState
+import io.mockk.every
+import io.mockk.mockk
+import kotlinx.coroutines.test.runTest
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+
+/**
+ * 타이머 저장층의 상태 전이를 메모리 DB로 검증합니다.
+ *
+ * 전이를 틀리면 서버에 없는 타이머에 수정 요청이 나가거나 삭제가 서버에 전달되지 않습니다
+ */
+@RunWith(RobolectricTestRunner::class)
+class TimerLocalDataSourceTest {
+    private lateinit var database: UndabangDatabase
+    private lateinit var preferenceManager: PreferenceManager
+    private lateinit var dataSource: TimerLocalDataSource
+
+    @Before
+    fun setUp() {
+        database = createInMemoryDatabase()
+        preferenceManager = mockk()
+        every { preferenceManager.getMemberId() } returns MEMBER_ID
+        dataSource = TimerLocalDataSource(database.timerDao(), preferenceManager)
+    }
+
+    @After
+    fun tearDown() {
+        database.close()
+    }
+
+    private val steps =
+        listOf(
+            CachedTimerStep(order = 1, name = "준비", time = 30),
+            CachedTimerStep(order = 2, name = "운동", time = 60),
+        )
+
+    private suspend fun markSynced(
+        localId: String,
+        serverId: Long,
+    ) {
+        val timer = database.timerDao().getSimpleTimer(MEMBER_ID, localId)!!
+        database.timerDao().upsertSimpleTimer(
+            timer.copy(serverId = serverId, syncState = SyncState.SYNCED, pendingEditId = null),
+        )
+    }
+
+    // ── 심플 타이머 ────────────────────────────────
+
+    @Test
+    fun `생성 - 생성 대기 상태와 요청 식별자를 남긴다`() =
+        runTest {
+            // When
+            val localId = dataSource.createSimpleTimer(time = 60)!!
+
+            // Then
+            val saved = database.timerDao().getSimpleTimer(MEMBER_ID, localId)!!
+            assertThat(saved.syncState).isEqualTo(SyncState.CREATE_PENDING)
+            assertThat(saved.serverId).isNull()
+            assertThat(saved.createRequestId).isNotEmpty()
+            assertThat(saved.editedAt).isGreaterThan(0L)
+        }
+
+    @Test
+    fun `수정 - 생성 대기 행은 생성 대기를 유지한다`() =
+        runTest {
+            // Given: 아직 서버에 없는 타이머
+            val localId = dataSource.createSimpleTimer(time = 60)!!
+            val created = database.timerDao().getSimpleTimer(MEMBER_ID, localId)!!
+
+            // When
+            dataSource.updateSimpleTimer(localId, time = 90)
+
+            // Then: 수정 대기로 바꾸면 서버에 없는 항목에 수정 요청이 나간다
+            val updated = database.timerDao().getSimpleTimer(MEMBER_ID, localId)!!
+            assertThat(updated.syncState).isEqualTo(SyncState.CREATE_PENDING)
+            assertThat(updated.time).isEqualTo(90)
+            assertThat(updated.createRequestId).isEqualTo(created.createRequestId)
+            assertThat(updated.pendingEditId).isNotNull()
+        }
+
+    @Test
+    fun `수정 - 서버에 있는 행은 수정 대기가 된다`() =
+        runTest {
+            // Given
+            val localId = dataSource.createSimpleTimer(time = 60)!!
+            markSynced(localId, serverId = 7L)
+
+            // When
+            dataSource.updateSimpleTimer(localId, time = 90)
+
+            // Then
+            val updated = database.timerDao().getSimpleTimer(MEMBER_ID, localId)!!
+            assertThat(updated.syncState).isEqualTo(SyncState.UPDATE_PENDING)
+            assertThat(updated.serverId).isEqualTo(7L)
+            assertThat(updated.pendingEditId).isNotNull()
+        }
+
+    @Test
+    fun `삭제 - 서버에 없는 행은 즉시 지운다`() =
+        runTest {
+            // Given
+            val localId = dataSource.createSimpleTimer(time = 60)!!
+
+            // When
+            dataSource.deleteSimpleTimer(localId)
+
+            // Then: 서버가 모르는 행이라 삭제를 알릴 필요가 없다
+            assertThat(database.timerDao().getSimpleTimer(MEMBER_ID, localId)).isNull()
+        }
+
+    @Test
+    fun `삭제 - 서버에 있는 행은 삭제 대기로 남는다`() =
+        runTest {
+            // Given
+            val localId = dataSource.createSimpleTimer(time = 60)!!
+            markSynced(localId, serverId = 7L)
+
+            // When
+            dataSource.deleteSimpleTimer(localId)
+
+            // Then
+            val deleted = database.timerDao().getSimpleTimer(MEMBER_ID, localId)!!
+            assertThat(deleted.syncState).isEqualTo(SyncState.DELETE_PENDING)
+            assertThat(dataSource.getSimpleTimers()).isEmpty()
+        }
+
+    @Test
+    fun `개수 - 삭제 대기 행은 세지 않는다`() =
+        runTest {
+            // Given
+            dataSource.createSimpleTimer(time = 30)
+            val toDelete = dataSource.createSimpleTimer(time = 60)!!
+            markSynced(toDelete, serverId = 7L)
+            dataSource.deleteSimpleTimer(toDelete)
+
+            // When & Then: 최대 6개 판정에 삭제 대기가 끼면 안 된다
+            assertThat(dataSource.countSimpleTimers()).isEqualTo(1)
+        }
+
+    @Test
+    fun `목록 - 시간 오름차순으로 나온다`() =
+        runTest {
+            // Given
+            dataSource.createSimpleTimer(time = 90)
+            dataSource.createSimpleTimer(time = 30)
+
+            // When & Then
+            assertThat(dataSource.getSimpleTimers().map { it.time }).containsExactly(30, 90).inOrder()
+        }
+
+    // ── 커스텀 타이머 ────────────────────────────────
+
+    @Test
+    fun `커스텀 생성 - 스텝 순서가 유지된다`() =
+        runTest {
+            // When
+            val localId = dataSource.createCustomTimer(name = "8세트", steps = steps)!!
+
+            // Then
+            val saved = dataSource.getCustomTimer(localId)!!
+            assertThat(saved.syncState).isEqualTo(SyncState.CREATE_PENDING)
+            assertThat(saved.steps.map { it.name }).containsExactly("준비", "운동").inOrder()
+        }
+
+    @Test
+    fun `커스텀 수정 - 스텝을 통째로 교체한다`() =
+        runTest {
+            // Given
+            val localId = dataSource.createCustomTimer(name = "8세트", steps = steps)!!
+
+            // When
+            dataSource.updateCustomTimer(
+                localId,
+                name = "10세트",
+                steps = listOf(CachedTimerStep(order = 1, name = "전력", time = 20)),
+            )
+
+            // Then: 이름과 스텝 목록이 판정 단위라 항목 단위로 병합하지 않는다
+            val updated = dataSource.getCustomTimer(localId)!!
+            assertThat(updated.name).isEqualTo("10세트")
+            assertThat(updated.steps).hasSize(1)
+        }
+
+    @Test
+    fun `대기 행 조회 - 동기화 완료 행은 빠진다`() =
+        runTest {
+            // Given
+            val pending = dataSource.createSimpleTimer(time = 30)!!
+            val synced = dataSource.createSimpleTimer(time = 60)!!
+            markSynced(synced, serverId = 7L)
+
+            // When & Then
+            assertThat(dataSource.getPendingSimpleTimers().map { it.localId }).containsExactly(pending)
+        }
+
+    // ── 계정 경계 ────────────────────────────────
+
+    @Test
+    fun `회원ID가 없으면 쓰지 않고 읽으면 빈 값이다`() =
+        runTest {
+            // Given
+            every { preferenceManager.getMemberId() } returns null
+
+            // When
+            val localId = dataSource.createSimpleTimer(time = 60)
+
+            // Then
+            assertThat(localId).isNull()
+            assertThat(dataSource.getSimpleTimers()).isEmpty()
+            assertThat(dataSource.countSimpleTimers()).isEqualTo(0)
+        }
+
+    @Test
+    fun `다른 계정의 타이머는 보이지 않는다`() =
+        runTest {
+            // Given
+            dataSource.createSimpleTimer(time = 60)
+            every { preferenceManager.getMemberId() } returns "member-b"
+
+            // When & Then
+            assertThat(dataSource.getSimpleTimers()).isEmpty()
+        }
+
+    companion object {
+        private const val MEMBER_ID = "member-a"
+    }
+}
diff --git a/data/src/test/java/com/project200/data/di/SchemaRecreatePolicyTest.kt b/data/src/test/java/com/project200/data/di/SchemaRecreatePolicyTest.kt
index cb56e0c1..d460614e 100644
--- a/data/src/test/java/com/project200/data/di/SchemaRecreatePolicyTest.kt
+++ b/data/src/test/java/com/project200/data/di/SchemaRecreatePolicyTest.kt
@@ -34,6 +34,7 @@ class SchemaRecreatePolicyTest {
         runTest {
             // Given: 캐시가 쌓인 DB
             var database = openDatabase()
+            val codeVersion = database.openHelper.readableDatabase.version
             database.exerciseCountDao().upsertAll(
                 listOf(ExerciseCountEntity(memberId = "member-a", date = date, count = 2)),
             )
@@ -44,10 +45,10 @@ class SchemaRecreatePolicyTest {
             val path = context.getDatabasePath(UndabangDatabase.DATABASE_NAME).absolutePath
             val mismatched =
                 SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READWRITE).use { raw ->
-                    raw.version = 2
+                    raw.version = codeVersion + 1
                     raw.version
                 }
-            assertThat(mismatched).isEqualTo(2)
+            assertThat(mismatched).isEqualTo(codeVersion + 1)
             database = openDatabase()
 
             // Then: 예외 없이 열리고 캐시는 비어 있다