Fixed time zone conversion with no TZ specified

Using .replace to set the current time zone appears to not handle
things correctly. The proper way to do this is apparently .localize.

homeassistant/util/dt.py

@@ -48,7 +48,7 @@ def as_utc(dattim):
     if dattim.tzinfo == UTC:
         return dattim
     elif dattim.tzinfo is None:
-        dattim = dattim.replace(tzinfo=DEFAULT_TIME_ZONE)
+        dattim = DEFAULT_TIME_ZONE.localize(dattim)
 
     return dattim.astimezone(UTC)
 
@@ -58,7 +58,7 @@ def as_local(dattim):
     if dattim.tzinfo == DEFAULT_TIME_ZONE:
         return dattim
     elif dattim.tzinfo is None:
-        dattim = dattim.replace(tzinfo=UTC)
+        dattim = UTC.localize(dattim)
 
     return dattim.astimezone(DEFAULT_TIME_ZONE)