diff --git a/zipline/finance/trading.py b/zipline/finance/trading.py
index cef7908d..7f33201d 100644
--- a/zipline/finance/trading.py
+++ b/zipline/finance/trading.py
@@ -115,6 +115,9 @@ class TradingEnvironment(object):
         self.early_closes = get_early_closes(self.first_trading_day,
                                              self.last_trading_day)
 
+        # The market open and close for the exchange.
+        self._times = None
+
     def __enter__(self, *args, **kwargs):
         global environment
         self.prev_environment = environment
@@ -130,6 +133,39 @@ class TradingEnvironment(object):
         # stack.
         return False
 
+    @property
+    def times(self):
+        if self._times is not None:
+            return self._times
+        else:
+            self._times = pd.DataFrame(index=self.trading_days,
+                                       columns=('market_open', 'market_close'))
+            for day in self.trading_days:
+                self._times['market_open'][day] = pd.Timestamp(
+                    datetime.datetime(
+                        year=day.year,
+                        month=day.month,
+                        day=day.day,
+                        hour=9,
+                        minute=31),
+                    tz=self.exchange_tz).tz_convert('UTC')
+
+                if day in self.early_closes:
+                    close_hour = 13
+                else:
+                    close_hour = 16
+
+                self._times['market_close'][day] = pd.Timestamp(
+                    datetime.datetime(
+                        year=day.year,
+                        month=day.month,
+                        day=day.day,
+                        hour=close_hour,
+                        minute=0),
+                    tz=self.exchange_tz).tz_convert('UTC')
+
+            return self._times
+
     def normalize_date(self, test_date):
         test_date = pd.Timestamp(test_date, tz='UTC')
         return pd.tseries.tools.normalize_date(test_date)
@@ -181,40 +217,19 @@ Last successful date: %s" % self.last_trading_day)
 
         return self.get_open_and_close(next_open)
 
-    def get_open_and_close(self, next_open):
+    def get_open_and_close(self, dt):
 
-        # creating a naive datetime with the correct hour,
-        # minute, and date. this will allow us to use pandas to
-        # shift the time between EST and UTC.
-        next_open = next_open.replace(
-            hour=9,
-            minute=31,
-            second=0,
-            microsecond=0,
-            tzinfo=None
-        )
-        # create a new Timestamp with the next_open naive date and
-        # the correct timezone for the exchange.
-        open_utc = self.exchange_dt_in_utc(next_open)
+        day = self.normalize_date(dt)
 
-        market_open = open_utc
-        market_close = (market_open
-                        + self.get_trading_day_duration(open_utc)
-                        - datetime.timedelta(minutes=1))
+        times_for_day = self.times.ix[day]
 
-        return market_open, market_close
+        return (times_for_day['market_open'],
+                times_for_day['market_close'])
 
     def market_minutes_for_day(self, midnight):
         market_open, market_close = self.get_open_and_close(midnight)
         return pd.date_range(market_open, market_close, freq='T')
 
-    def get_trading_day_duration(self, trading_day):
-        trading_day = self.normalize_date(trading_day)
-        if trading_day in self.early_closes:
-            return self.early_close_trading_day
-
-        return self.full_trading_day
-
     def trading_day_distance(self, first_date, second_date):
         first_date = self.normalize_date(first_date)
         second_date = self.normalize_date(second_date)