diff --git a/.env.example b/.env.example
index 4f73c18..376fcb6 100644
--- a/.env.example
+++ b/.env.example
@@ -34,8 +34,10 @@ STORAGE_DIR=./data
 MAX_UPLOAD_MB=32
 
 # Scheduled metadata-only DB backups (no image blobs). On by default, weekly.
-# BACKUP_INTERVAL accepts a Go duration (e.g. 168h, 24h); set 0 to disable.
-BACKUP_DIR=./data/backups
+# Files are named hsa_sqlite_backup_YYYY_MM_DD.db (one per day).
+# BACKUP_INTERVAL sets the frequency: a Go duration (e.g. 168h weekly, 24h daily,
+# 72h every 3 days); set 0 to disable.
+BACKUP_DIR=./data/dbbackup
 BACKUP_INTERVAL=168h
 BACKUP_KEEP=8
 
diff --git a/internal/backup/backup.go b/internal/backup/backup.go
index 129fe02..f0ebf3f 100644
--- a/internal/backup/backup.go
+++ b/internal/backup/backup.go
@@ -22,57 +22,46 @@ type Snapshotter interface {
 }
 
 const (
-	prefix = "hsa-backup-"
+	prefix = "hsa_sqlite_backup_"
 	suffix = ".db"
-	stamp  = "2006-01-02-150405"
+	stamp  = "2006_01_02" // yyyy_mm_dd — one backup per day
 )
 
-// Schedule runs metadata-only backups into dir every `every`, keeping the most
-// recent `keep`. It blocks until ctx is cancelled, so run it in a goroutine.
+// Schedule runs metadata-only backups into dir, attempting one on start and then
+// every `every`, keeping the most recent `keep`. It blocks until ctx is cancelled,
+// so run it in a goroutine. `now` is injected for testability (pass time.Now).
 //
-// On start it backs up immediately unless a backup younger than `every` already
-// exists — so frequent restarts don't spam the directory, and a gap longer than
-// the interval is covered right away. `now` is injected for testability (pass
-// time.Now).
+// Backups are idempotent per day (date-only filenames): a write whose dated file
+// already exists is a no-op, so frequent restarts — or intervals shorter than a
+// day — never duplicate or spam, they just settle at one backup per day.
 func Schedule(ctx context.Context, s Snapshotter, dir string, every time.Duration, keep int, now func() time.Time) {
 	if err := os.MkdirAll(dir, 0o700); err != nil {
 		log.Printf("backup: cannot create %s: %v (backups disabled)", dir, err)
 		return
 	}
 	for {
-		timer := time.NewTimer(untilNext(dir, every, now()))
+		if err := writeBackup(s, dir, now()); err != nil {
+			log.Printf("backup: %v", err)
+		} else if err := prune(dir, keep); err != nil {
+			log.Printf("backup prune: %v", err)
+		}
+		timer := time.NewTimer(every)
 		select {
 		case <-ctx.Done():
 			timer.Stop()
 			return
 		case <-timer.C:
 		}
-		if err := writeBackup(s, dir, now()); err != nil {
-			log.Printf("backup: %v", err)
-			continue
-		}
-		if err := prune(dir, keep); err != nil {
-			log.Printf("backup prune: %v", err)
-		}
 	}
 }
 
-// untilNext is how long to wait before the next backup: zero if none exists or the
-// newest is already older than `every`, otherwise the remaining time.
-func untilNext(dir string, every time.Duration, now time.Time) time.Duration {
-	newest := newestBackup(dir)
-	if newest.IsZero() {
-		return 0
-	}
-	if elapsed := now.Sub(newest); elapsed < every {
-		return every - elapsed
-	}
-	return 0
-}
-
 func writeBackup(s Snapshotter, dir string, now time.Time) error {
 	name := prefix + now.UTC().Format(stamp) + suffix
-	if err := s.SnapshotTo(filepath.Join(dir, name), false); err != nil {
+	dest := filepath.Join(dir, name)
+	if _, err := os.Stat(dest); err == nil {
+		return nil // today's backup already exists (date-only name) — nothing to do
+	}
+	if err := s.SnapshotTo(dest, false); err != nil {
 		return fmt.Errorf("write %s: %w", name, err)
 	}
 	log.Printf("backup: wrote %s", name)
@@ -96,19 +85,6 @@ func backupFiles(dir string) []string {
 	return names
 }
 
-func newestBackup(dir string) time.Time {
-	names := backupFiles(dir)
-	if len(names) == 0 {
-		return time.Time{}
-	}
-	last := strings.TrimSuffix(strings.TrimPrefix(names[len(names)-1], prefix), suffix)
-	t, err := time.Parse(stamp, last) // layout has no zone → parsed as UTC
-	if err != nil {
-		return time.Time{}
-	}
-	return t
-}
-
 // prune deletes the oldest backups beyond the most recent `keep`.
 func prune(dir string, keep int) error {
 	names := backupFiles(dir)
diff --git a/internal/backup/backup_test.go b/internal/backup/backup_test.go
index 65ab711..ac80a8d 100644
--- a/internal/backup/backup_test.go
+++ b/internal/backup/backup_test.go
@@ -18,7 +18,7 @@ func (f *fakeSnap) SnapshotTo(dest string, includeBlobs bool) error {
 	return os.WriteFile(dest, []byte("snap"), 0o600)
 }
 
-func TestWriteBackupAndNewest(t *testing.T) {
+func TestWriteBackup_NamesAndSameDayNoOp(t *testing.T) {
 	dir := t.TempDir()
 	s := &fakeSnap{}
 	now := time.Date(2026, 6, 10, 9, 0, 0, 0, time.UTC)
@@ -27,35 +27,19 @@ func TestWriteBackupAndNewest(t *testing.T) {
 		t.Fatal(err)
 	}
 	files := backupFiles(dir)
-	if len(files) != 1 || files[0] != "hsa-backup-2026-06-10-090000.db" {
+	if len(files) != 1 || files[0] != "hsa_sqlite_backup_2026_06_10.db" {
 		t.Fatalf("files = %v", files)
 	}
-	if got := newestBackup(dir); !got.Equal(now) {
-		t.Errorf("newestBackup = %v, want %v", got, now)
+
+	// A same-day second call is a no-op: no error, still one file, no re-snapshot.
+	if err := writeBackup(s, dir, now.Add(time.Hour)); err != nil {
+		t.Fatal(err)
 	}
-}
-
-func TestUntilNext(t *testing.T) {
-	dir := t.TempDir()
-	every := 168 * time.Hour
-	now := time.Date(2026, 6, 10, 9, 0, 0, 0, time.UTC)
-
-	// No backups yet → back up immediately.
-	if d := untilNext(dir, every, now); d != 0 {
-		t.Errorf("empty dir: untilNext = %v, want 0", d)
+	if files := backupFiles(dir); len(files) != 1 {
+		t.Errorf("same-day re-run produced %v, want 1 file", files)
 	}
-
-	// A fresh backup → wait nearly the full interval.
-	_ = writeBackup(&fakeSnap{}, dir, now.Add(-1*time.Hour))
-	if d := untilNext(dir, every, now); d <= 0 || d > every {
-		t.Errorf("fresh backup: untilNext = %v, want ~167h", d)
-	}
-
-	// An old backup → back up now.
-	dir2 := t.TempDir()
-	_ = writeBackup(&fakeSnap{}, dir2, now.Add(-200*time.Hour))
-	if d := untilNext(dir2, every, now); d != 0 {
-		t.Errorf("stale backup: untilNext = %v, want 0", d)
+	if s.calls != 1 {
+		t.Errorf("SnapshotTo called %d times, want 1 (second was a no-op)", s.calls)
 	}
 }
 
@@ -74,7 +58,7 @@ func TestPruneKeepsMostRecent(t *testing.T) {
 		t.Fatalf("after prune: %v", files)
 	}
 	// The two newest (Jan 04, Jan 05) survive.
-	if !strings.Contains(files[0], "2026-01-04") || !strings.Contains(files[1], "2026-01-05") {
+	if !strings.Contains(files[0], "2026_01_04") || !strings.Contains(files[1], "2026_01_05") {
 		t.Errorf("wrong files kept: %v", files)
 	}
 }
@@ -91,7 +75,7 @@ func TestScheduleRunsOnceThenStops(t *testing.T) {
 	// Wait for the immediate first backup to land.
 	deadline := time.Now().Add(2 * time.Second)
 	for time.Now().Before(deadline) {
-		if _, err := os.Stat(filepath.Join(dir, "hsa-backup-2026-06-10-090000.db")); err == nil {
+		if _, err := os.Stat(filepath.Join(dir, "hsa_sqlite_backup_2026_06_10.db")); err == nil {
 			return
 		}
 		time.Sleep(10 * time.Millisecond)
diff --git a/internal/config/config.go b/internal/config/config.go
index f68862f..e8ce6fd 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -93,7 +93,7 @@ func Load() (Config, error) {
 
 	// Scheduled metadata-only DB backups (on by default, weekly). Set
 	// BACKUP_INTERVAL=0 to disable.
-	c.BackupDir = envOr("BACKUP_DIR", "./data/backups")
+	c.BackupDir = envOr("BACKUP_DIR", "./data/dbbackup")
 	c.BackupEvery = 7 * 24 * time.Hour
 	if v := strings.TrimSpace(os.Getenv("BACKUP_INTERVAL")); v != "" {
 		if d, err := time.ParseDuration(v); err == nil {
diff --git a/spec.md b/spec.md
index 0324c9c..7a58765 100644
--- a/spec.md
+++ b/spec.md
@@ -317,11 +317,12 @@ external cron job.
     backup excludes image blobs from BOTH receipts and attachments, so it is tiny.
     The on-disk files and the full-blob export (/export/db) remain the source for
     the images themselves.
-  - On by default, weekly. Config: BACKUP_DIR (default ./data/backups),
-    BACKUP_INTERVAL (Go duration, default 168h; set 0 to disable), BACKUP_KEEP
-    (most-recent copies to retain, default 8).
-  - Files are named hsa-backup-<UTC timestamp>.db so they sort chronologically;
-    older copies beyond BACKUP_KEEP are pruned.
+  - On by default, weekly. Config: BACKUP_DIR (default ./data/dbbackup),
+    BACKUP_INTERVAL (Go duration sets the frequency, default 168h; set 0 to
+    disable), BACKUP_KEEP (most-recent copies to retain, default 8).
+  - Files are named hsa_sqlite_backup_<YYYY_MM_DD>.db — one per day, sorting
+    chronologically; older copies beyond BACKUP_KEEP are pruned. A same-day re-run
+    is a no-op (the dated file already exists).
   - Restart-safe: on startup it backs up immediately only if the newest existing
     backup is older than the interval, so frequent restarts don't spam the dir and
     a long gap is covered right away. Runs in a background goroutine for the life