Fix review summary for DST (#20770)

* Fix review summary for DST

* Fix

frigate/util/builtin.py

@@ -15,12 +15,9 @@ from collections.abc import Mapping
 from multiprocessing.sharedctypes import Synchronized
 from pathlib import Path
 from typing import Any, Dict, Optional, Tuple, Union
-from zoneinfo import ZoneInfoNotFoundError
 
 import numpy as np
-import pytz
 from ruamel.yaml import YAML
-from tzlocal import get_localzone
 
 from frigate.const import REGEX_HTTP_CAMERA_USER_PASS, REGEX_RTSP_CAMERA_USER_PASS
 
@@ -157,17 +154,6 @@ def load_labels(path: Optional[str], encoding="utf-8", prefill=91):
         return labels
 
 
-def get_tz_modifiers(tz_name: str) -> Tuple[str, str, float]:
-    seconds_offset = (
-        datetime.datetime.now(pytz.timezone(tz_name)).utcoffset().total_seconds()
-    )
-    hours_offset = int(seconds_offset / 60 / 60)
-    minutes_offset = int(seconds_offset / 60 - hours_offset * 60)
-    hour_modifier = f"{hours_offset} hour"
-    minute_modifier = f"{minutes_offset} minute"
-    return hour_modifier, minute_modifier, seconds_offset
-
-
 def to_relative_box(
     width: int, height: int, box: Tuple[int, int, int, int]
 ) -> Tuple[int | float, int | float, int | float, int | float]:
@@ -298,34 +284,6 @@ def find_by_key(dictionary, target_key):
     return None
 
 
-def get_tomorrow_at_time(hour: int) -> datetime.datetime:
-    """Returns the datetime of the following day at 2am."""
-    try:
-        tomorrow = datetime.datetime.now(get_localzone()) + datetime.timedelta(days=1)
-    except ZoneInfoNotFoundError:
-        tomorrow = datetime.datetime.now(datetime.timezone.utc) + datetime.timedelta(
-            days=1
-        )
-        logger.warning(
-            "Using utc for maintenance due to missing or incorrect timezone set"
-        )
-
-    return tomorrow.replace(hour=hour, minute=0, second=0).astimezone(
-        datetime.timezone.utc
-    )
-
-
-def is_current_hour(timestamp: int) -> bool:
-    """Returns if timestamp is in the current UTC hour."""
-    start_of_next_hour = (
-        datetime.datetime.now(datetime.timezone.utc).replace(
-            minute=0, second=0, microsecond=0
-        )
-        + datetime.timedelta(hours=1)
-    ).timestamp()
-    return timestamp < start_of_next_hour
-
-
 def clear_and_unlink(file: Path, missing_ok: bool = True) -> None:
     """clear file then unlink to avoid space retained by file descriptors."""
     if not missing_ok and not file.exists():

frigate/util/time.py

@@ -0,0 +1,100 @@
+"""Time utilities."""
+
+import datetime
+import logging
+from typing import Tuple
+from zoneinfo import ZoneInfoNotFoundError
+
+import pytz
+from tzlocal import get_localzone
+
+logger = logging.getLogger(__name__)
+
+
+def get_tz_modifiers(tz_name: str) -> Tuple[str, str, float]:
+    seconds_offset = (
+        datetime.datetime.now(pytz.timezone(tz_name)).utcoffset().total_seconds()
+    )
+    hours_offset = int(seconds_offset / 60 / 60)
+    minutes_offset = int(seconds_offset / 60 - hours_offset * 60)
+    hour_modifier = f"{hours_offset} hour"
+    minute_modifier = f"{minutes_offset} minute"
+    return hour_modifier, minute_modifier, seconds_offset
+
+
+def get_tomorrow_at_time(hour: int) -> datetime.datetime:
+    """Returns the datetime of the following day at 2am."""
+    try:
+        tomorrow = datetime.datetime.now(get_localzone()) + datetime.timedelta(days=1)
+    except ZoneInfoNotFoundError:
+        tomorrow = datetime.datetime.now(datetime.timezone.utc) + datetime.timedelta(
+            days=1
+        )
+        logger.warning(
+            "Using utc for maintenance due to missing or incorrect timezone set"
+        )
+
+    return tomorrow.replace(hour=hour, minute=0, second=0).astimezone(
+        datetime.timezone.utc
+    )
+
+
+def is_current_hour(timestamp: int) -> bool:
+    """Returns if timestamp is in the current UTC hour."""
+    start_of_next_hour = (
+        datetime.datetime.now(datetime.timezone.utc).replace(
+            minute=0, second=0, microsecond=0
+        )
+        + datetime.timedelta(hours=1)
+    ).timestamp()
+    return timestamp < start_of_next_hour
+
+
+def get_dst_transitions(
+    tz_name: str, start_time: float, end_time: float
+) -> list[tuple[float, float]]:
+    """
+    Find DST transition points and return time periods with consistent offsets.
+
+    Args:
+        tz_name: Timezone name (e.g., 'America/New_York')
+        start_time: Start timestamp (UTC)
+        end_time: End timestamp (UTC)
+
+    Returns:
+        List of (period_start, period_end, seconds_offset) tuples representing
+        continuous periods with the same UTC offset
+    """
+    try:
+        tz = pytz.timezone(tz_name)
+    except pytz.UnknownTimeZoneError:
+        # If timezone is invalid, return single period with no offset
+        return [(start_time, end_time, 0)]
+
+    periods = []
+    current = start_time
+
+    # Get initial offset
+    dt = datetime.datetime.utcfromtimestamp(current).replace(tzinfo=pytz.UTC)
+    local_dt = dt.astimezone(tz)
+    prev_offset = local_dt.utcoffset().total_seconds()
+    period_start = start_time
+
+    # Check each day for offset changes
+    while current <= end_time:
+        dt = datetime.datetime.utcfromtimestamp(current).replace(tzinfo=pytz.UTC)
+        local_dt = dt.astimezone(tz)
+        current_offset = local_dt.utcoffset().total_seconds()
+
+        if current_offset != prev_offset:
+            # Found a transition - close previous period
+            periods.append((period_start, current, prev_offset))
+            period_start = current
+            prev_offset = current_offset
+
+        current += 86400  # Check daily
+
+    # Add final period
+    periods.append((period_start, end_time, prev_offset))
+
+    return periods