Convert datetimes to aware datetimes with UTC.

Naive datetimes will now be interpreted as local time throughout
the library.

discord/utils.py

@@ -25,6 +25,7 @@ DEALINGS IN THE SOFTWARE.
 import array
 import asyncio
 import collections.abc
+from typing import Optional, overload
 import unicodedata
 from base64 import b64encode
 from bisect import bisect_left
@@ -103,9 +104,17 @@ class SequenceProxy(collections.abc.Sequence):
     def count(self, value):
         return self.__proxied.count(value)
 
-def parse_time(timestamp):
+@overload
+def parse_time(timestamp: None) -> None:
+    ...
+
+@overload
+def parse_time(timestamp: str) -> datetime.datetime:
+    ...
+
+def parse_time(timestamp: Optional[str]) -> Optional[datetime.datetime]:
     if timestamp:
-        return datetime.datetime(*map(int, re.split(r'[^\d]', timestamp.replace('+00:00', ''))))
+        return datetime.datetime.fromisoformat(timestamp)
     return None
 
 def copy_doc(original):
@@ -168,7 +177,7 @@ def oauth_url(client_id, permissions=None, guild=None, redirect_uri=None, scopes
     return url
 
 
-def snowflake_time(id):
+def snowflake_time(id: int) -> datetime.datetime:
     """
     Parameters
     -----------
@@ -178,25 +187,34 @@ def snowflake_time(id):
     Returns
     --------
     :class:`datetime.datetime`
-        The creation date in UTC of a Discord snowflake ID."""
-    return datetime.datetime.utcfromtimestamp(((id >> 22) + DISCORD_EPOCH) / 1000)
+        An aware datetime in UTC representing the creation time of the snowflake.
+    """
+    timestamp = ((id >> 22) + DISCORD_EPOCH) / 1000
+    return datetime.datetime.utcfromtimestamp(timestamp).replace(tzinfo=datetime.timezone.utc)
 
-def time_snowflake(datetime_obj, high=False):
+def time_snowflake(dt: datetime.datetime, high: bool = False) -> int:
     """Returns a numeric snowflake pretending to be created at the given date.
 
-    When using as the lower end of a range, use ``time_snowflake(high=False) - 1`` to be inclusive, ``high=True`` to be exclusive
-    When using as the higher end of a range, use ``time_snowflake(high=True)`` + 1 to be inclusive, ``high=False`` to be exclusive
+    When using as the lower end of a range, use ``time_snowflake(high=False) - 1``
+    to be inclusive, ``high=True`` to be exclusive.
+
+    When using as the higher end of a range, use ``time_snowflake(high=True) + 1``
+    to be inclusive, ``high=False`` to be exclusive
 
     Parameters
     -----------
-    datetime_obj: :class:`datetime.datetime`
-        A timezone-naive datetime object representing UTC time.
+    dt: :class:`datetime.datetime`
+        A datetime object to convert to a snowflake.
+        If naive, the timezone is assumed to be local time.
     high: :class:`bool`
         Whether or not to set the lower 22 bit to high or low.
-    """
-    unix_seconds = (datetime_obj - type(datetime_obj)(1970, 1, 1)).total_seconds()
-    discord_millis = int(unix_seconds * 1000 - DISCORD_EPOCH)
 
+    Returns
+    --------
+    :class:`int`
+        The snowflake representing the time given.
+    """
+    discord_millis = int(dt.timestamp() * 1000 - DISCORD_EPOCH)
     return (discord_millis << 22) + (2**22-1 if high else 0)
 
 def find(predicate, seq):
@@ -374,12 +392,12 @@ async def sleep_until(when, result=None):
     -----------
     when: :class:`datetime.datetime`
         The timestamp in which to sleep until. If the datetime is naive then
-        it is assumed to be in UTC.
+        it is assumed to be local time.
     result: Any
         If provided is returned to the caller when the coroutine completes.
     """
     if when.tzinfo is None:
-        when = when.replace(tzinfo=datetime.timezone.utc)
+        when = when.astimezone()
     now = datetime.datetime.now(datetime.timezone.utc)
     delta = (when - now).total_seconds()
     while delta > MAX_ASYNCIO_SECONDS: