Upload utils.py

api/utils.py

@@ -1,5 +1,25 @@
 from datetime import datetime, time, timedelta
 
+def _eastern_utc_offset(now_utc):
+    """
+    Returns the UTC offset in hours for Eastern time (EST=-5, EDT=-4).
+    Uses North American DST rules: starts second Sunday in March at 2 AM EST (07:00 UTC),
+    ends first Sunday in November at 2 AM EDT (06:00 UTC).
+    """
+    year = now_utc.year
+    from datetime import timezone
+    march_1 = datetime(year, 3, 1, tzinfo=timezone.utc)
+    first_sun_mar = march_1 + timedelta(days=(6 - march_1.weekday()) % 7)
+    dst_start = first_sun_mar + timedelta(weeks=1, hours=7)
+
+    nov_1 = datetime(year, 11, 1, tzinfo=timezone.utc)
+    first_sun_nov = nov_1 + timedelta(days=(6 - nov_1.weekday()) % 7)
+    dst_end = first_sun_nov + timedelta(hours=6)
+
+    if dst_start <= now_utc < dst_end:
+        return 4  # EDT
+    return 5  # EST
+
 def hms_to_seconds(hms_str):
     """Converts GTFS 'HH:MM:SS' (e.g. '25:30:00') to total seconds from midnight."""
     h, m, s = map(int, hms_str.split(':'))
@@ -22,13 +42,14 @@ def get_service_day_start_ts():
             import pytz
             eastern_tz = pytz.timezone("America/Toronto")
         except ImportError:
-            # Last resort: hardcoded UTC-5 (EST), no DST handling
+            # Last resort: pure-Python DST-aware Eastern offset
             now_utc = datetime.now(timezone.utc)
-            if now_utc.hour < 9:  # 4 AM Eastern = 9 AM UTC (EST)
+            utc_offset = _eastern_utc_offset(now_utc)
+            if now_utc.hour < (4 + utc_offset):  # 4 AM Eastern in UTC
                 service_date = now_utc.date() - timedelta(days=1)
             else:
                 service_date = now_utc.date()
-            service_start_utc = datetime.combine(service_date, time.min, tzinfo=timezone.utc) + timedelta(hours=5)
+            service_start_utc = datetime.combine(service_date, time.min, tzinfo=timezone.utc) + timedelta(hours=utc_offset)
             return int(service_start_utc.timestamp())
     
     # Get current UTC time and convert to Eastern