Refactor timestamp conversion to use timezone-aware datetime

Author: hackdna

src/forest/poplar/functions/time.py

@@ -124,8 +124,7 @@ def to_readable(timestamp: int, to_format: str,
     try:
         if isinstance(to_tz, str):
             to_tz = pytz.timezone(to_tz)
-        datetime_date = datetime.datetime.utcfromtimestamp(timestamp / 1000)
-        utc_dt = pytz.utc.localize(datetime_date)
+        utc_dt = datetime.datetime.fromtimestamp(timestamp / 1000, tz=pytz.UTC)
         local_dt = utc_dt.astimezone(to_tz)
         readable = local_dt.strftime(to_format)
         return readable

src/forest/poplar/legacy/common_funcs.py

@@ -56,10 +56,7 @@ def stamp2datetime(stamp: Union[float, int], tz_str: str) -> list:
          specified tz
     """
     loc_tz = timezone(tz_str)
-
-    utc = timezone("UTC")
-    utc_dt = utc.localize(datetime.utcfromtimestamp(stamp))
-
+    utc_dt = datetime.fromtimestamp(stamp, timezone("UTC"))
     loc_dt = utc_dt.astimezone(loc_tz)
     return [
         loc_dt.year, loc_dt.month, loc_dt.day,