fix: use tz-aware meeting datetime to decide when to show ical link (#4429)

* refactor: reimplement Meeting.end_datetime() using datetime_from_date helper

* fix: use tz-aware meeting datetime to decide when to show ical link

ietf/meeting/models.py

@@ -138,11 +138,14 @@ class Meeting(models.Model):
     def end_date(self):
         return self.get_meeting_date(self.days-1)
 
+    def start_datetime(self):
+        """Start-of-day on meeting.date in meeting time zone"""
+        return datetime_from_date(self.date, self.tz())
+
     def end_datetime(self):
-        """Datetime of the first instant _after_ the meeting's last day"""
-        return self.tz().localize(
-            datetime.datetime.combine(self.get_meeting_date(self.days), datetime.time())
-        )
+        """Datetime of the first instant _after_ the meeting's last day in meeting time zone"""
+        return datetime_from_date(self.get_meeting_date(self.days), self.tz())
+
     def get_00_cutoff(self):
         start_date = datetime.datetime(year=self.date.year, month=self.date.month, day=self.date.day, tzinfo=pytz.utc)
         importantdate = self.importantdate_set.filter(name_id='idcutoff').first()

ietf/templates/meeting/session_details.html

@@ -14,7 +14,7 @@
         <br>
         <small class="text-muted">{{ acronym }}</small>
     </h1>
-    {% if meeting.date >= thisweek %}
+    {% if meeting.start_datetime >= thisweek %}
         <a class="regular float-end"
            title="icalendar entry for {{ acronym }}@{{ meeting.number }}"
            aria-label="icalendar entry for {{ acronym }}@{{ meeting.number }}"