don't use system tz, display timestamps as UTC

no particular reason, just one less dependency, and it goes further
towards my idyllic world where everyone is on UTC and there are no
timezones

incorporealcms/pages.py

@@ -7,7 +7,6 @@ import re
 from flask import Blueprint, Markup, abort
 from flask import current_app as app
 from flask import redirect, request, send_from_directory
-from tzlocal import get_localzone
 
 from incorporealcms.lib import get_meta_str, init_md, render
 
@@ -51,7 +50,7 @@ def handle_markdown_file_path(resolved_path):
     try:
         logger.debug("opening resolved path '%s'", resolved_path)
         with app.open_instance_resource(resolved_path, 'r') as entry_file:
-            mtime = datetime.datetime.fromtimestamp(os.path.getmtime(entry_file.name), get_localzone())
+            mtime = datetime.datetime.fromtimestamp(os.path.getmtime(entry_file.name), tz=datetime.timezone.utc)
             entry = entry_file.read()
         logger.debug("resolved path '%s' read", resolved_path)
     except OSError: