MAINT: Using zone attribute of tzinfo instead of string

zipline/finance/trading.py

@@ -219,7 +219,7 @@ Last successful date: %s" % self.market_open)
         # create a new Delorean with the next_open naive date and
         # the correct timezone for the exchange.
         open_delorean = Delorean(next_open, self.exchange_tz)
-        open_utc = open_delorean.shift("UTC").datetime
+        open_utc = open_delorean.shift(pytz.utc.zone).datetime
 
         market_open = open_utc
         market_close = market_open + self.get_trading_day_duration(open_utc)

zipline/utils/factory.py

@@ -118,14 +118,14 @@ check treasury and benchmark data in findb, and re-run the test."""
 
 def get_next_trading_dt(current, interval):
     naive = current.replace(tzinfo=None)
-    delo = Delorean(naive, "UTC")
+    delo = Delorean(naive, pytz.utc.zone)
     ex_tz = trading.environment.exchange_tz
     next_dt = delo.shift(ex_tz).datetime
 
     while True:
         next_dt = next_dt + interval
         next_delo = Delorean(next_dt.replace(tzinfo=None), ex_tz)
-        next_utc = next_delo.shift("UTC").datetime
+        next_utc = next_delo.shift(pytz.utc.zone).datetime
         if trading.environment.is_market_hours(next_utc):
             break
 

zipline/utils/tradingcalendar.py

@@ -22,8 +22,8 @@ from dateutil import rrule
 from delorean import Delorean
 
 start = datetime(1990, 1, 1, tzinfo=pytz.utc)
-end_dln = Delorean(datetime.utcnow(), 'UTC')
-end_dln.shift('US/Eastern').truncate('day').shift('UTC')
+end_dln = Delorean(datetime.utcnow(), pytz.utc.zone)
+end_dln.shift('US/Eastern').truncate('day').shift(pytz.utc.zone)
 end = end_dln.datetime - timedelta(days=1)