Clean up timestamps.py and add a test.

analytics/management/commands/update_analytics_counts.py

@@ -15,7 +15,6 @@ from django.conf import settings
 
 from analytics.models import RealmCount, UserCount
 from analytics.lib.counts import COUNT_STATS, logger, process_count_stat
-from zerver.lib.timestamp import datetime_to_string, is_timezone_aware
 from zerver.models import UserProfile, Message
 
 from typing import Any
@@ -30,7 +29,7 @@ class Command(BaseCommand):
         parser.add_argument('--time', '-t',
                             type=str,
                             help='Update stat tables from current state to --time. Defaults to the current time.',
-                            default=datetime_to_string(timezone.now()))
+                            default=timezone.now().isoformat())
         parser.add_argument('--utc',
                             type=bool,
                             help="Interpret --time in UTC.",
@@ -61,7 +60,7 @@ class Command(BaseCommand):
         if options['utc']:
             fill_to_time = fill_to_time.replace(tzinfo=timezone.utc)
 
-        if not (is_timezone_aware(fill_to_time)):
+        if fill_to_time.tzinfo is None:
             raise ValueError("--time must be timezone aware. Maybe you meant to use the --utc option?")
 
         logger.info("Starting updating analytics counts through %s" % (fill_to_time,))

analytics/models.py

@@ -3,7 +3,7 @@ from django.utils import timezone
 
 from zerver.models import Realm, UserProfile, Stream, Recipient
 from zerver.lib.str_utils import ModelReprMixin
-from zerver.lib.timestamp import datetime_to_UTC, floor_to_day
+from zerver.lib.timestamp import floor_to_day
 
 import datetime
 
@@ -29,7 +29,7 @@ class FillState(ModelReprMixin, models.Model):
 def installation_epoch():
     # type: () -> datetime.datetime
     earliest_realm_creation = Realm.objects.aggregate(models.Min('date_created'))['date_created__min']
-    return floor_to_day(datetime_to_UTC(earliest_realm_creation))
+    return floor_to_day(earliest_realm_creation)
 
 def last_successful_fill(property):
     # type: (str) -> Optional[datetime.datetime]

zerver/lib/timestamp.py

@@ -4,37 +4,27 @@ import datetime
 import calendar
 from django.utils import timezone
 
-def is_timezone_aware(datetime_object):
-    # type: (datetime.datetime) -> bool
-    return datetime_object.tzinfo is not None
-
-def datetime_to_UTC(datetime_object):
+def floor_to_hour(dt):
     # type: (datetime.datetime) -> datetime.datetime
-    if is_timezone_aware(datetime_object):
-        return datetime_object.astimezone(timezone.utc)
-    return datetime_object.replace(tzinfo=timezone.utc)
+    return datetime.datetime(*dt.timetuple()[:4]) \
+                   .replace(tzinfo=dt.tzinfo)
 
-def floor_to_hour(datetime_object):
+def floor_to_day(dt):
     # type: (datetime.datetime) -> datetime.datetime
-    return datetime.datetime(*datetime_object.timetuple()[:4]) \
-                   .replace(tzinfo=datetime_object.tzinfo)
+    return datetime.datetime(*dt.timetuple()[:3]) \
+                   .replace(tzinfo=dt.tzinfo)
 
-def floor_to_day(datetime_object):
+def ceiling_to_hour(dt):
     # type: (datetime.datetime) -> datetime.datetime
-    return datetime.datetime(*datetime_object.timetuple()[:3]) \
-                   .replace(tzinfo=datetime_object.tzinfo)
-
-def ceiling_to_hour(datetime_object):
-    # type: (datetime.datetime) -> datetime.datetime
-    floor = floor_to_hour(datetime_object)
-    if floor == datetime_object:
+    floor = floor_to_hour(dt)
+    if floor == dt:
         return floor
     return floor + datetime.timedelta(hours=1)
 
-def ceiling_to_day(datetime_object):
+def ceiling_to_day(dt):
     # type: (datetime.datetime) -> datetime.datetime
-    floor = floor_to_day(datetime_object)
-    if floor == datetime_object:
+    floor = floor_to_day(dt)
+    if floor == dt:
         return floor
     return floor + datetime.timedelta(days=1)
 
@@ -42,12 +32,11 @@ def timestamp_to_datetime(timestamp):
     # type: (float) -> datetime.datetime
     return datetime.datetime.fromtimestamp(float(timestamp), tz=timezone.utc)
 
-def datetime_to_timestamp(datetime_object):
-    # type: (datetime.datetime) -> int
-    return calendar.timegm(datetime_object.timetuple())
+class TimezoneNotUTCException(Exception):
+    pass
 
-def datetime_to_string(datetime_object):
-    # type: (datetime.datetime) -> str
-    assert is_timezone_aware(datetime_object)
-    date_string = datetime_object.strftime('%Y-%m-%d %H:%M:%S%z')
-    return date_string
+def datetime_to_timestamp(dt):
+    # type: (datetime.datetime) -> int
+    if dt.tzinfo is None or dt.tzinfo.utcoffset(dt) != timezone.utc.utcoffset(dt):
+        raise TimezoneNotUTCException("Datetime %s to be converted does not have a UTC timezone." % (dt,))
+    return calendar.timegm(dt.timetuple())

zerver/tests/test_timestamp.py

@@ -0,0 +1,31 @@
+from __future__ import absolute_import
+
+from django.utils import timezone
+
+from zerver.lib.test_classes import ZulipTestCase
+from zerver.lib.timestamp import floor_to_hour, floor_to_day, ceiling_to_hour, \
+    ceiling_to_day, timestamp_to_datetime, datetime_to_timestamp, \
+    TimezoneNotUTCException
+
+from datetime import datetime, timedelta
+from dateutil import parser
+import pytz
+
+from six.moves import zip
+
+class TestTimestamp(ZulipTestCase):
+    def test_datetime_and_timestamp_conversions(self):
+        # type: () -> None
+        timestamp = 1483228800
+        for dt in [
+                parser.parse('2017-01-01 00:00:00.123 UTC'),
+                parser.parse('2017-01-01 00:00:00.123').replace(tzinfo=timezone.utc),
+                parser.parse('2017-01-01 00:00:00.123').replace(tzinfo=pytz.utc)]:
+            self.assertEqual(timestamp_to_datetime(timestamp), dt-timedelta(microseconds=123000))
+            self.assertEqual(datetime_to_timestamp(dt), timestamp)
+
+        for dt in [
+                parser.parse('2017-01-01 00:00:00.123+01:00'),
+                parser.parse('2017-01-01 00:00:00.123')]:
+            with self.assertRaises(TimezoneNotUTCException):
+                datetime_to_timestamp(dt)