first commit

backend/app/periods.py

@@ -0,0 +1,35 @@
+from datetime import datetime, timedelta
+from zoneinfo import ZoneInfo
+
+TZ = ZoneInfo("Asia/Shanghai")
+DAY_CUTOFF_HOUR = 8
+
+
+def now_shanghai() -> datetime:
+    return datetime.now(TZ)
+
+
+def _align_cutoff(dt: datetime) -> datetime:
+    cutoff = dt.replace(hour=DAY_CUTOFF_HOUR, minute=0, second=0, microsecond=0)
+    if dt < cutoff:
+        cutoff -= timedelta(days=1)
+    return cutoff
+
+
+def get_yesterday_period(now: datetime | None = None) -> tuple[datetime, datetime]:
+    """[D-1 08:00, D 08:00) in Shanghai time."""
+    now = now or now_shanghai()
+    end = _align_cutoff(now)
+    start = end - timedelta(days=1)
+    return start, end
+
+
+def get_today_period(now: datetime | None = None) -> tuple[datetime, datetime]:
+    """[D 08:00, now) in Shanghai time."""
+    now = now or now_shanghai()
+    start = _align_cutoff(now)
+    return start, now
+
+
+def to_ms(dt: datetime) -> int:
+    return int(dt.timestamp() * 1000)