email_notifications: Convert datetime to local date string.

zerver/lib/email_notifications.py

@@ -16,6 +16,7 @@ import lxml.html
 from bs4 import BeautifulSoup
 from django.conf import settings
 from django.contrib.auth import get_backends
+from django.utils.timezone import get_current_timezone_name as timezone_get_current_timezone_name
 from django.utils.timezone import now as timezone_now
 from django.utils.translation import gettext as _
 from django.utils.translation import override as override_language
@@ -32,6 +33,7 @@ from zerver.lib.queue import queue_event_on_commit
 from zerver.lib.send_email import EMAIL_DATE_FORMAT, FromAddress, send_future_email
 from zerver.lib.soft_deactivation import soft_reactivate_if_personal_notification
 from zerver.lib.tex import change_katex_to_raw_latex
+from zerver.lib.timestamp import format_datetime_to_string
 from zerver.lib.timezone import canonicalize_timezone
 from zerver.lib.topic import get_topic_display_name, get_topic_resolution_and_bare_name
 from zerver.lib.url_encoding import (
@@ -183,6 +185,25 @@ def fix_spoilers_in_text(content: str, language: str) -> str:
     return "\n".join(output)
 
 
+def convert_time_to_local_timezone(fragment: lxml.html.HtmlElement, user: UserProfile) -> None:
+    user_tz = user.timezone or timezone_get_current_timezone_name()
+    time_elements = fragment.findall(".//time")
+
+    for time_elem in time_elements:
+        datetime_str = time_elem.get("datetime")
+        if not datetime_str:
+            # We expect there to always be a datetime attribute.
+            continue  # nocoverage
+        try:
+            dt_utc = timezone_now().strptime(datetime_str, "%Y-%m-%dT%H:%M:%S%z")
+            dt_local = dt_utc.astimezone(zoneinfo.ZoneInfo(canonicalize_timezone(user_tz)))
+            formatted_time = format_datetime_to_string(dt_local, user.twenty_four_hour_time)
+            time_elem.text = formatted_time
+        except Exception as e:
+            logger.warning("Failed to convert time element '%s': %s", datetime_str, e)
+            continue
+
+
 def add_quote_prefix_in_text(content: str) -> str:
     """
     We add quote prefix ">" to each line of the message in plain text
@@ -260,6 +281,7 @@ def build_message_list(
         fix_emojis(fragment, user.emojiset)
         fix_spoilers_in_html(fragment, user.default_language)
         change_katex_to_raw_latex(fragment)
+        convert_time_to_local_timezone(fragment, user)
 
         html = Markup(lxml.html.tostring(fragment, encoding="unicode"))
         if sender:

zerver/tests/test_message_notification_emails.py

@@ -1404,6 +1404,58 @@ class TestMessageNotificationEmails(ZulipTestCase):
             mail.outbox[0].alternatives[0][0],
         )
 
+    def test_datetime_conversion_in_missed_message_content(self) -> None:
+        hamlet = self.example_user("hamlet")
+
+        get_or_create_direct_message_group(id_list=[hamlet.id])
+
+        # Normal message with timestamp.
+        msg_id = self.send_personal_message(
+            hamlet, hamlet, "Meeting at <time:2025-09-30T09:30:00-07:00>", read_by_sender=False
+        )
+
+        self.handle_missedmessage_emails(
+            hamlet.id,
+            {msg_id: MissedMessageData(trigger=NotificationTriggers.DIRECT_MESSAGE)},
+        )
+
+        assert isinstance(mail.outbox[0], EmailMultiAlternatives)
+        self.assertEqual(mail.outbox[0].subject, "DMs with King Hamlet")
+        assert isinstance(mail.outbox[0].alternatives[0][0], str)
+        # Sender name is not appended for missed 1:1 direct messages
+        self.assertEqual(
+            "> Meeting at <time:2025-09-30T09:30:00-07:00>\n\n--\n\nReply", mail.outbox[0].body[:56]
+        )
+        self.assertIn(
+            '<p>Meeting at <time datetime="2025-09-30T16:30:00Z">Tuesday, September 30, 2025 at 04:30 PM UTC</time></p>',
+            mail.outbox[0].alternatives[0][0],
+        )
+
+        # The timestamp is not formatted correctly.
+        msg_id = self.send_personal_message(
+            hamlet, hamlet, "Meeting at <time:2025-09-30T09:30:00-07:00>", read_by_sender=False
+        )
+
+        with (
+            mock.patch(
+                "zerver.lib.email_notifications.format_datetime_to_string",
+                side_effect=ValueError("Invalid datetime format"),
+            ),
+            self.assertLogs(level="WARNING") as m,
+        ):
+            self.handle_missedmessage_emails(
+                hamlet.id,
+                {msg_id: MissedMessageData(trigger=NotificationTriggers.DIRECT_MESSAGE)},
+            )
+
+        self.assertEqual(
+            m.output,
+            [
+                "WARNING:zerver.lib.email_notifications:Failed to convert time element "
+                "'2025-09-30T16:30:00Z': Invalid datetime format",
+            ],
+        )
+
     def test_multiple_missed_personal_messages(self) -> None:
         hamlet = self.example_user("hamlet")
         msg_id_1 = self.send_personal_message(