diff --git a/modules/extensions.py b/modules/extensions.py
index 1063e5eb7..134176e3d 100644
--- a/modules/extensions.py
+++ b/modules/extensions.py
@@ -1,6 +1,6 @@
 from __future__ import annotations
 import os
-from datetime import datetime
+from datetime import datetime, timezone
 import git
 from modules import shared, errors
 from modules.paths import extensions_dir, extensions_builtin_dir
@@ -11,6 +11,30 @@ if not os.path.exists(extensions_dir):
     os.makedirs(extensions_dir)
 
 
+def parse_isotime(time_string: str) -> datetime:
+    # If Python minimum version is 3.11+, this function can be replaced with datetime.fromisoformat()
+    trimmed = time_string.rstrip("Z")
+    if "." in trimmed:
+        trimmed = trimmed.split(".")[0]
+    match len(trimmed):
+        case 16:
+            return datetime.strptime(trimmed, "%Y-%m-%dT%H:%M").replace(tzinfo=timezone.utc)
+        case 19:
+            return datetime.strptime(trimmed, "%Y-%m-%dT%H:%M:%S").replace(tzinfo=timezone.utc)
+        case _:
+            raise ValueError(f"Unexpected time string format: '{time_string}'")
+
+
+def format_dt(d: datetime) -> str:
+    if d.tzinfo is None:
+        return d.strftime('%Y-%m-%d %H:%M')
+    return d.astimezone(timezone.utc).strftime('%Y-%m-%d %H:%M:%S') # Ensure UTC time is shown (just in case)
+
+
+def ts2utc(timestamp: int) -> datetime:
+    return datetime.fromtimestamp(timestamp, timezone.utc)
+
+
 def active():
     if shared.opts.disable_all_extensions == "all":
         return []
@@ -106,8 +130,8 @@ class Extension:
         self.branch = None
         self.remote = None
         self.have_info_from_repo = False
-        self.mtime = 0
-        self.ctime = 0
+        self.mtime = "2000-01-01T00:00Z"
+        self.ctime = "2000-01-01T00:00Z"
 
     def read_info(self, force=False):
         if self.have_info_from_repo and not force:
@@ -142,7 +166,7 @@ class Extension:
                 except Exception:
                     self.branch = 'unknown'
                 self.commit_hash = head.hexsha
-                self.version = f"<p>{self.commit_hash[:8]}</p><p>{datetime.fromtimestamp(self.commit_date).strftime('%a %b%d %Y %H:%M')}</p>"
+                self.version = f"<p>{self.commit_hash[:8]}</p><p>{format_dt(ts2utc(self.commit_date))}</p>"
             except Exception as ex:
                 shared.log.error(f"Extension: failed reading data from git repo={self.name}: {ex}")
                 self.remote = None
diff --git a/modules/ui_extensions.py b/modules/ui_extensions.py
index c9271780e..a6c5ca3ec 100644
--- a/modules/ui_extensions.py
+++ b/modules/ui_extensions.py
@@ -3,7 +3,7 @@ import json
 import shutil
 import errno
 import html
-from datetime import datetime, timedelta
+from datetime import datetime, timezone, timedelta
 import gradio as gr
 from modules import extensions, shared, paths, errors, ui_symbols, call_queue
 
@@ -37,12 +37,9 @@ def get_installed(ext):
 def list_extensions():
     global extensions_list # pylint: disable=global-statement
     fn = os.path.join(paths.script_path, "html", "extensions.json")
-    extensions_list = shared.readfile(fn, silent=True) or []
-    if type(extensions_list) != list:
-        shared.log.warning(f'Invalid extensions list: file="{fn}"')
-        extensions_list = []
+    extensions_list = shared.readfile(fn, silent=True, as_type="list")
     if len(extensions_list) == 0:
-        shared.log.info('Extension list is empty: refresh required')
+        shared.log.info("Extension List: No information found. Refresh required.")
     found = []
     for ext in extensions.extensions:
         ext.read_info()
@@ -111,10 +108,10 @@ def check_updates(_id_task, disable_list, search_text, sort_column):
                 ext.git_fetch()
                 ext.read_info()
                 commit_date = ext.commit_date or 1577836800
-                shared.log.info(f'Extensions updated: {ext.name} {ext.commit_hash[:8]} {datetime.utcfromtimestamp(commit_date)}')
+                shared.log.info(f'Extensions updated: {ext.name} {ext.commit_hash[:8]} {extensions.format_dt(extensions.ts2utc(commit_date))}')
             else:
                 commit_date = ext.commit_date or 1577836800
-                shared.log.debug(f'Extensions no update available: {ext.name} {ext.commit_hash[:8]} {datetime.utcfromtimestamp(commit_date)}')
+                shared.log.debug(f'Extensions no update available: {ext.name} {ext.commit_hash[:8]} {extensions.format_dt(extensions.ts2utc(commit_date))}')
         except FileNotFoundError as e:
             if 'FETCH_HEAD' not in str(e):
                 raise
@@ -232,10 +229,10 @@ def update_extension(extension_path, search_text, sort_column):
                 ext.git_fetch()
                 ext.read_info()
                 commit_date = ext.commit_date or 1577836800
-                shared.log.info(f'Extensions updated: {ext.name} {ext.commit_hash[:8]} {datetime.utcfromtimestamp(commit_date)}')
+                shared.log.info(f'Extensions updated: {ext.name} {ext.commit_hash[:8]} {extensions.format_dt(extensions.ts2utc(commit_date))}')
             else:
                 commit_date = ext.commit_date or 1577836800
-                shared.log.info(f'Extensions no update available: {ext.name} {ext.commit_hash[:8]} {datetime.utcfromtimestamp(commit_date)}')
+                shared.log.info(f'Extensions no update available: {ext.name} {ext.commit_hash[:8]} {extensions.format_dt(extensions.ts2utc(commit_date))}')
         except FileNotFoundError as e:
             if 'FETCH_HEAD' not in str(e):
                 raise
@@ -308,13 +305,13 @@ def create_html(search_text, sort_column):
         ext['enabled'] = installed.enabled if installed is not None else ''
         ext['remote'] = installed.remote if installed is not None else None
         ext['path'] = installed.path if installed is not None else ''
-        ext['sort_default'] = f"{'1' if ext['is_builtin'] else '0'}{'1' if ext['installed'] else '0'}{ext.get('updated', '2000-01-01T00:00')}"
+        ext['sort_default'] = f"{'1' if ext['is_builtin'] else '0'}{'1' if ext['installed'] else '0'}{ext.get('updated', '2000-01-01T00:00Z')}"
     sort_reverse, sort_function = sort_ordering[sort_column]
 
     def dt(x: str):
         val = ext.get(x, None)
         try:
-            return datetime.fromisoformat(val[:-1]).strftime('%a %b%d %Y %H:%M') if val is not None else "N/A"
+            return extensions.format_dt(extensions.parse_isotime(val)) if val is not None else "N/A"
         except Exception:
             return 'N/A'
 
@@ -322,22 +319,23 @@ def create_html(search_text, sort_column):
     for ext in sorted(extensions_list, key=sort_function, reverse=sort_reverse):
         installed = get_installed(ext)
         author = ''
-        updated = datetime.timestamp(datetime.now())
+        updated = datetime.now(timezone.utc) # TZ-aware
         try:
             if 'github' in ext['url']:
                 author = 'Author: ' + ext['url'].split('/')[-2].split(':')[-1] if '/' in ext['url'] else ext['url'].split(':')[1].split('/')[0]
-                updated = datetime.timestamp(datetime.fromisoformat(ext.get('updated', '2000-01-01T00:00:00.000Z').rstrip('Z')))
+                updated = extensions.parse_isotime(ext.get('updated', '2000-01-01T00:00:00Z')) # TZ-aware
             else:
                 debug(f'Extension not from github: name={ext["name"]} url={ext["url"]}')
         except Exception as e:
             debug(f'Extension get updated error: name={ext["name"]} url={ext["url"]} {e}')
-        update_available = (installed is not None) and (ext['remote'] is not None) and (updated > ext['commit_date'])
+        local_ver_date = extensions.ts2utc(ext['commit_date']) # TZ-aware
+        update_available = (installed is not None) and (not ext['is_builtin']) and (ext['remote'] is not None) and (updated > local_ver_date) # TZ-aware
         if update_available:
-            debug(f'Extension update available: name={ext["name"]} updated={updated}/{datetime.utcfromtimestamp(updated)} commit={ext["commit_date"]}/{datetime.utcfromtimestamp(ext["commit_date"])}')
+            debug(f'Extension update available: name={ext["name"]} updated={extensions.format_dt(updated)} commit={extensions.format_dt(local_ver_date)}') # TZ-aware
         ext['sort_user'] = f"{'0' if ext['is_builtin'] else '1'}{'1' if ext['installed'] else '0'}{ext.get('name', '')}"
-        ext['sort_enabled'] = f"{'0' if ext['enabled'] else '1'}{'1' if ext['is_builtin'] else '0'}{'1' if ext['installed'] else '0'}{ext.get('updated', '2000-01-01T00:00')}"
-        ext['sort_update'] = f"{'1' if update_available else '0'}{'1' if ext['installed'] else '0'}{ext.get('updated', '2000-01-01T00:00')}"
-        delta = datetime.now() - datetime.fromisoformat(ext.get('created', '2000-01-01T00:00Z')[:-1])
+        ext['sort_enabled'] = f"{'0' if ext['enabled'] else '1'}{'1' if ext['is_builtin'] else '0'}{'1' if ext['installed'] else '0'}{ext.get('updated', '2000-01-01T00:00Z')}"
+        ext['sort_update'] = f"{'1' if update_available else '0'}{'1' if ext['installed'] else '0'}{ext.get('updated', '2000-01-01T00:00Z')}"
+        delta = datetime.now(timezone.utc) - extensions.parse_isotime(ext.get('created', '2000-01-01T00:00Z')) # TZ-aware to prep for 3.11+ datetime.fromisoformat() behavior
         ext['sort_trending'] = round(ext.get('stars', 0) / max(delta.days, 5), 1)
         tags = ext.get("tags", [])
         if not isinstance(tags, list):
@@ -399,7 +397,7 @@ def create_html(search_text, sort_column):
             else:
                 status = f"<div style='cursor:help;width:1em;' title='Unknown status'>{ui_symbols.svg_bullet.color('#008EBC')}</div>"
         else:
-            if updated < datetime.timestamp(datetime.now() - timedelta(6*30)):
+            if updated < datetime.now(timezone.utc) - timedelta(6*30): # TZ-aware
                 status = f"<div style='cursor:help;width:1em;' title='Unmaintained'>{ui_symbols.svg_bullet.color('#C000CF')}</div>"
             else:
                 status = f"<div style='cursor:help;width:1em;' title='No info'>{ui_symbols.svg_bullet.color('#7C7C7C')}</div>"