halfhour table period is too close to halfday (4 columns until rescale).

Replace with quarterhour, do not change plot period.

apachedex/__init__.py

@@ -964,9 +964,9 @@ def _asMinuteString(timestamp):
   day, month, year = dt_date.split('/')
   return '%s/%02i/%s %s:%s' % (year, MONTH_VALUE_DICT[month], day, hour, minute)
 
-def _asHalfHourString(timestamp):
+def _asQuarterHourString(timestamp):
   prefix, minute = timestamp.rsplit(':', 1)
-  return '%s:%02i' % (prefix, int(minute) // 30 * 30)
+  return '%s:%02i' % (prefix, int(minute) // 15 * 15)
 
 # Key: argument (represents table granularity)
 # Value:
@@ -1055,10 +1055,10 @@ period_parser = {
     lambda x: x.replace(minute=x.minute // 30 * 30),
     lambda x: 1,
   ),
-  'halfhour': (
+  'quarterhour': (
     # graph/table ratio: 30
     _asMinuteString,
-    _asHalfHourString,
+    _asQuarterHourString,
     'minute',
     '%Y/%m/%d %H:%M',
     timedelta(seconds=60),