diff --git a/backend/routers/sleep.py b/backend/routers/sleep.py
index ec8f056..4dd9a1a 100644
--- a/backend/routers/sleep.py
+++ b/backend/routers/sleep.py
@@ -545,11 +545,12 @@ async def import_apple_health_sleep(
                 night['awake_minutes']
             )
 
-            # Prepare JSONB segments
+            # Prepare JSONB segments with full datetime
             sleep_segments = [
                 {
                     'phase': seg['phase'],
-                    'start': seg['start'].strftime('%H:%M'),
+                    'start': seg['start'].isoformat(),  # Full datetime: 2026-03-21T22:30:00
+                    'end': seg['end'].isoformat(),      # Full datetime: 2026-03-21T23:15:00
                     'duration_min': seg['duration_min']
                 }
                 for seg in night['segments']