diff --git a/internal/backend/sync.go b/internal/backend/sync.go
index dcd9202..db5f339 100644
--- a/internal/backend/sync.go
+++ b/internal/backend/sync.go
@@ -45,12 +45,12 @@ type SyncResponse struct {
 	SoundtracksChangedContent []string          `json:"soundtracks_changed_content"`
 	SoundtracksRemoved        []string          `json:"soundtracks_removed"`
 	CatchedErrors             []string          `json:"catched_errors"`
-	TotalTime                 string            `json:"total_time"`
+	TotalTime                 string            `json:"total_time" doc:"How long the sync took, as minutes and seconds, e.g. \"02:15\""`
 }
 
 type ProgressResponse struct {
 	Progress  string `json:"progress"`
-	TimeSpent string `json:"time_spent"`
+	TimeSpent string `json:"time_spent" doc:"How long the sync has been running, as minutes and seconds, e.g. \"02:15\""`
 }
 
 type SoundtrackStatus int
@@ -164,8 +164,11 @@ func (s *SyncService) ResetDB(ctx context.Context) error {
 	return s.q.ClearSoundtracks(ctx)
 }
 
+// formatDuration shows d as minutes and seconds, "MM:SS". A sync longer than an hour
+// keeps counting minutes, e.g. "75:03".
 func formatDuration(d time.Duration) string {
-	return time.Time{}.Add(d).Format("15:04:05")
+	seconds := int(d / time.Second)
+	return fmt.Sprintf("%02d:%02d", seconds/60, seconds%60)
 }
 
 // syncRun holds the state of a single sync.
diff --git a/internal/backend/sync_test.go b/internal/backend/sync_test.go
index 090252d..30962d5 100644
--- a/internal/backend/sync_test.go
+++ b/internal/backend/sync_test.go
@@ -401,7 +401,10 @@ func TestResetDB(t *testing.T) {
 }
 
 func TestFormatDuration(t *testing.T) {
-	assert.Equal(t, "01:02:03", formatDuration(time.Hour+2*time.Minute+3*time.Second))
+	assert.Equal(t, "00:00", formatDuration(0))
+	assert.Equal(t, "00:07", formatDuration(7*time.Second+900*time.Millisecond), "parts of a second are left out")
+	assert.Equal(t, "02:15", formatDuration(2*time.Minute+15*time.Second))
+	assert.Equal(t, "62:03", formatDuration(time.Hour+2*time.Minute+3*time.Second), "minutes keep counting past an hour")
 }
 
 func TestSyncKeepsAlternativeNamesAndCover(t *testing.T) {