activity: Show the time the data is from.

I've wanted this when looking at a tab from the day before.
Also provides the date and time in UTC, which is handy for
interpreting some of the data.

Pretty sure this is not the world's cleanest way to do this in the
front-end code.  It'll do for now.

analytics/views.py

@@ -287,6 +287,8 @@ def get_realm_day_counts() -> Dict[str, Dict[str, str]]:
     return result
 
 def realm_summary_table(realm_minutes: Dict[str, float]) -> str:
+    now = timezone_now()
+
     query = '''
         SELECT
             realm.string_id,
@@ -397,7 +399,7 @@ def realm_summary_table(realm_minutes: Dict[str, float]) -> str:
 
     for row in rows:
         row['date_created_day'] = row['date_created'].strftime('%Y-%m-%d')
-        row['age_days'] = int((timezone_now() - row['date_created']).total_seconds()
+        row['age_days'] = int((now - row['date_created']).total_seconds()
                               / 86400)
         row['is_new'] = row['age_days'] < 12 * 7
 
@@ -455,7 +457,8 @@ def realm_summary_table(realm_minutes: Dict[str, float]) -> str:
 
     content = loader.render_to_string(
         'analytics/realm_summary_table.html',
-        dict(rows=rows, num_active_sites=num_active_sites)
+        dict(rows=rows, num_active_sites=num_active_sites,
+             now=now.strftime('%Y-%m-%dT%H:%M:%SZ'))
     )
     return content
 

templates/analytics/realm_summary_table.html

@@ -1,5 +1,13 @@
 <h2 style="text-align: center;">{{ num_active_sites }} active sites</h2>
 
+<p id="utctime" style="text-align: center;"></p>
+<p id="localtime" style="text-align: center;"></p>
+<script type="text/javascript">
+    var now = moment('{{ now }}');
+    $('#utctime')[0].innerHTML = moment.utc(now).format('YYYY-MM-DD HH:mm') + 'Z';
+    $('#localtime')[0].innerHTML = '(' + now.format('YYYY-MM-DD HH:mm ZZ') + ')';
+</script>
+
 <ul>
     <li><strong>active (site)</strong> - has ≥5 DAUs</li>
     <li>sites are listed if ≥1 users active in last 2 weeks</li>