Use utc timezones consistently

Author: lovelydinosaur

mkdocs/utils/__init__.py

@@ -53,10 +53,10 @@ def get_build_timestamp(*, pages: Collection[Page] | None = None) -> int:
     if pages:
         # Lexicographic comparison is OK for ISO date.
         date_string = max(p.update_date for p in pages)
-        dt = datetime.fromisoformat(date_string)
+        dt = datetime.fromisoformat(date_string).replace(tzinfo=timezone.utc)
     else:
         dt = get_build_datetime()
-    return max(int(dt.timestamp()), 0)
+    return int(dt.timestamp())
 
 
 def get_build_datetime() -> datetime: