Migrate to some newer date/time APIs

app/src/main/java/eu/kanade/tachiyomi/data/backup/BackupCreateJob.kt

@@ -25,7 +25,7 @@ import tachiyomi.domain.backup.service.BackupPreferences
 import tachiyomi.domain.storage.service.StorageManager
 import uy.kohesive.injekt.Injekt
 import uy.kohesive.injekt.api.get
-import java.util.Date
+import java.time.Instant
 import java.util.concurrent.TimeUnit
 import kotlin.time.Duration.Companion.minutes
 import kotlin.time.toJavaDuration
@@ -52,7 +52,7 @@ class BackupCreateJob(private val context: Context, workerParams: WorkerParamete
         return try {
             val location = BackupCreator(context).createBackup(uri, flags, isAutoBackup)
             if (isAutoBackup) {
-                backupPreferences.lastAutoBackupTimestamp().set(Date().time)
+                backupPreferences.lastAutoBackupTimestamp().set(Instant.now().toEpochMilli())
             } else {
                 notifier.showBackupComplete(UniFile.fromUri(context, location.toUri())!!)
             }