help: Update time zone article for update local time zone banner.

Updates the help center article for changing your time zone to
document the banner for updating the local time zone to match
the computer's time zone.

help/change-your-timezone.md

@@ -1,19 +1,60 @@
 # Change your time zone
 
-Zulip always uses your computer's time zone for displaying dates and
-timestamps (note that you need to reload Zulip after changing your
-computer's time zone for changes to take effect).
+Zulip uses the time zone configured on your computer or mobile device for
+displaying dates and times, such as when a message was sent.
 
-By default, Zulip also indirectly displays your time zone to others, via the
-**Local time** field of your [user profile](/help/view-someones-profile).
-You can change the time zone Zulip displays to others.
+You can [configure your **local time**](#configure-your-local-time) as it's
+shown to other users in your [user card](/help/user-cards) and
+[profile](/help/view-someones-profile). When your local time doesn't match your
+computer's time zone, the Zulip web and desktop apps display a banner offering
+to update it. If you don't want to see this banner, you can [hide
+it](#hide-banner-when-time-zones-dont-match).
 
-### Change your time zone
+## Configure your local time
 
 {start_tabs}
 
+{tab|desktop-web}
+
 {settings_tab|profile}
 
-2. Under **Profile**, select a time zone.
+1. Under **Profile**, select a time zone.
 
 {end_tabs}
+
+
+## Configure time zone used by Zulip to display dates and times
+
+{start_tabs}
+
+1. Configure the time zone on your computer or mobile device.
+
+1. Reload Zulip.
+
+{end_tabs}
+
+## Hide banner when time zones don't match
+
+If you local time in Zulip differs from your device's time zone (for example,
+you changed your computer's time zone while traveling), you'll see a banner in
+the web and desktop apps offering to update your local time to match your
+computer's current time zone.
+
+You can choose to permanently hide this banner.
+
+{start_tabs}
+
+{tab|desktop-web}
+
+{settings_tab|profile}
+
+2. Under **Profile**, toggle **Offer to update to my computer's
+   time zone**.
+
+{end_tabs}
+
+## Related articles
+
+* [User cards](/help/user-cards)
+* [View someone's profile](/help/view-someones-profile)
+* [Edit your profile](/help/edit-your-profile)