diff --git a/tests/test_transforms.py b/tests/test_transforms.py
index b9420633..2a13e4d7 100644
--- a/tests/test_transforms.py
+++ b/tests/test_transforms.py
@@ -100,9 +100,9 @@ class FinanceTransformsTestCase(TestCase):
     def test_moving_average(self):
         
         mavg = StatefulTransform(
-            MovingAverage, 
-            timedelta(days = 2), 
-            ['price', 'volume']
+            MovingAverage,          
+            fields = ['price', 'volume'],
+            delta = timedelta(days = 2), 
         ) 
         
         transformed = list(mavg.transform(self.source))
diff --git a/zipline/gens/mavg.py b/zipline/gens/mavg.py
index 1978f92e..21aa0bd0 100644
--- a/zipline/gens/mavg.py
+++ b/zipline/gens/mavg.py
@@ -13,17 +13,39 @@ class MovingAverage(object):
     maintain a sid's average volume as well as its average price.)
     """
 
-    def __init__(self, delta, fields):
-        self.delta = delta
+    def __init__(self, fields, market_aware, days = None, delta = None):
+
         self.fields = fields
+        self.market_aware = market_aware
+
+        self.delta = delta
+        self.days = days
+
+        # Market-aware mode only works with full-day windows.
+        if self.market_aware:
+            assert self.days and not self.delta,\
+                "Market-aware mode only works with full-day windows."
+
+        # Non-market-aware mode requires a timedelta.
+        else:
+            assert self.delta and not self.days, \
+                "Non-market-aware mode requires a timedelta."
+        
         # No way to pass arguments to the defaultdict factory, so we
         # need to define a method to generate the correct EventWindows.
         self.sid_windows = defaultdict(self.create_window)
 
     def create_window(self):
-        """Factory method for self.sid_windows."""
-        return MovingAverageEventWindow(self.delta, self.fields)
-
+        """
+        Factory method for self.sid_windows.
+        """
+        return MovingAverageEventWindow(
+            self.fields, 
+            self.market_aware, 
+            self.days, 
+            self.delta
+        )
+    
     def update(self, event):
         """
         Update the event window for this event's sid.  Return an ndict
@@ -45,11 +67,11 @@ class MovingAverageEventWindow(EventWindow):
     MovingAverage transform.
     """
 
-    def __init__(self, delta, fields):
+    def __init__(self, fields, market_aware, days, delta):
 
         # Call the superclass constructor to set up base EventWindow
         # infrastructure.
-        EventWindow.__init__(self, delta)
+        EventWindow.__init__(self, market_aware, days, delta)
 
         # We maintain a dictionary of totals for each of our tracked
         # fields.
diff --git a/zipline/gens/tradesimulation.py b/zipline/gens/tradesimulation.py
index 972f44e8..522d80da 100644
--- a/zipline/gens/tradesimulation.py
+++ b/zipline/gens/tradesimulation.py
@@ -74,7 +74,7 @@ class TradeSimulationClient(object):
         # Pipe the events with transactions to perf. This will remove
         # the txn field added by TransactionSimulator and replace it
         # with a portfolio object to be passed to the user's
-        # algorithm. Also adds a PERF_MESSAGE field which is usually
+        # algorithm. Also adds a perf_message field which is usually
         # none, but contains an update message once per day.
         perf_tracker = StatefulTransform(
             PerformanceTracker,
diff --git a/zipline/gens/transform.py b/zipline/gens/transform.py
index 202acc0f..09f074ae 100644
--- a/zipline/gens/transform.py
+++ b/zipline/gens/transform.py
@@ -2,9 +2,10 @@
 Generator versions of transforms.
 """
 import types
+import pytz
 
 from copy import deepcopy
-from datetime import datetime
+from datetime import datetime, timedelta
 from collections import deque, defaultdict
 from numbers import Number
 from abc import ABCMeta, abstractmethod
@@ -149,6 +150,9 @@ class EventWindow:
     window.  Calls self.handle_remove(event) for each event removed
     from the window.  Subclass these methods along with init(*args,
     **kwargs) to calculate metrics over the window.  
+    
+    The market_aware flag is used to toggle whether the eventwindow
+    calculates
 
     See zipline/gens/mavg.py and zipline/gens/vwap.py for example
     implementations of moving average and volume-weighted average
@@ -157,10 +161,31 @@ class EventWindow:
     # Mark this as an abstract base class.
     __metaclass__ = ABCMeta
 
-    def __init__(self, delta):
+    def __init__(self, market_aware, days = None, delta = None):
+
+        self.market_aware = market_aware
+        self.days = days
+        self.delta = delta
+
         self.ticks  = deque()
-        self.delta  = delta
+
+        # Market-aware mode only works with full-day windows.
+        if self.market_aware:
+            assert self.days and not self.delta,\
+                "Market-aware mode only works with full-day windows."
+
+        # Non-market-aware mode requires a timedelta.
+        else:
+            assert self.delta and not self.days, \
+                "Non-market-aware mode requires a timedelta."
         
+        # Set the behavior for dropping events from the back of the
+        # event window.
+        if self.market_aware:
+            self.drop_condition = self.out_of_market_window
+        else:
+            self.drop_condition = self.out_of_timedelta
+
     @abstractmethod
     def handle_add(self, event):
         raise NotImplementedError()
@@ -174,22 +199,36 @@ class EventWindow:
 
     def update(self, event):
         self.assert_well_formed(event)
+
         # Add new event and increment totals.
         self.ticks.append(event)
+
+        # Subclasses should override handle_add to define behavior for
+        # adding new ticks.
         self.handle_add(event)
 
-        # Clear out expired event.
+        # Clear out any expired events. drop_condition changes depending
+        # on whether or not we are running in market_aware mode.
         #
-        #           newest               oldest
-        #             |                    |
-        #             V                    V
-        while (self.ticks[-1].dt - self.ticks[0].dt) > self.delta:
+        #                              oldest               newest
+        #                                |                    |
+        #                                V                    V
+        while self.drop_condition(self.ticks[0].dt, self.ticks[-1].dt):
+            
             # popleft removes and returns the oldest tick in self.ticks
             popped = self.ticks.popleft()
+
             # Subclasses should override handle_remove to define
             # behavior for removing ticks.
             self.handle_remove(popped)
             
+    def out_of_market_window(self, oldest, newest):
+        return trading_days_between(oldest, newest) >= self.days
+
+    def out_of_delta(self, oldest, newest):
+        return (newest - oldest) >= self.delta
+
+
     # All event windows expect to receive events with datetime fields
     # that arrive in sorted order.
     def assert_well_formed(self, event):
@@ -200,3 +239,6 @@ class EventWindow:
             # Something is wrong if new event is older than previous.
             assert event.dt >= self.ticks[-1].dt, \
                 "Events arrived out of order in EventWindow: %s -> %s" % (event, self.ticks[0])
+
+
+
diff --git a/zipline/gens/vwap.py b/zipline/gens/vwap.py
index 029284c1..5a0947d8 100644
--- a/zipline/gens/vwap.py
+++ b/zipline/gens/vwap.py
@@ -9,16 +9,33 @@ class VWAP(object):
     """
     Class that maintains a dictionary from sids to VWAPEventWindows.
     """
-    def __init__(self, delta):
+    def __init__(self, market_aware, delta=None, days=None):
+
+        self.market_aware = market_aware
         self.delta = delta
+        self.days = days
+        
+        # Market-aware mode only works with full-day windows.
+        if self.market_aware:
+            assert self.days and not self.delta,\
+                "Market-aware mode only works with full-day windows."
+
+        # Non-market-aware mode requires a timedelta.
+        else:
+            assert self.delta and not self.days, \
+                "Non-market-aware mode requires a timedelta."
 
         # No way to pass arguments to the defaultdict factory, so we
         # need to define a method to generate the correct EventWindows.
         self.sid_windows = defaultdict(self.create_window)
-
+        
     def create_window(self):
         """Factory method for self.sid_windows."""
-        return VWAPEventWindow(self.delta)
+        return VWAPEventWindow(
+            self.market_aware, 
+            days = self.days, 
+            delta = self.delta
+        )
 
     def update(self, event):
         """
@@ -31,14 +48,13 @@ class VWAP(object):
         window.update(event)
         return window.get_vwap()
 
-
 class VWAPEventWindow(EventWindow):
     """
     Iteratively maintains a vwap for a single sid over a given
     timedelta.
     """
-    def __init__(self, delta):
-        EventWindow.__init__(self, delta)
+    def __init__(self, market_aware, days=None, delta=None):
+        EventWindow.__init__(self, market_aware, days, delta)
         self.flux = 0.0
         self.totalvolume = 0.0
 
diff --git a/zipline/utils/tradingcalendar.py b/zipline/utils/tradingcalendar.py
index c7aa9152..7742b714 100644
--- a/zipline/utils/tradingcalendar.py
+++ b/zipline/utils/tradingcalendar.py
@@ -84,8 +84,7 @@ def earlier_in_day(d1, d2):
     """
     Return true if d1 falls earlier in its own day than d2.
     """
-    d1 = d1.replace(year = d2.year, day = d2.day)
-    return d1 < d2
+    return d1.time() < d2.time()
 
 WEEKDAYS = [rrule.MO, rrule.TU, rrule.WE, rrule.TH, rrule.FR]
 
@@ -97,7 +96,8 @@ market_opens_with_holidays = rrule.rrule(
     byhour = 14,
     byminute = 30,
     cache = True,
-    dtstart=datetime(1970, 1, 1, tzinfo = pytz.utc),
+    dtstart=datetime(2000, 1, 1, tzinfo = pytz.utc),
+    until=datetime(2014 , 1, 1, tzinfo = pytz.utc)
 )
 
 # Recurrence rule that generates all market closes since Jan 1, 1970.
@@ -108,7 +108,8 @@ market_closes_with_holidays = rrule.rrule(
     byhour = 21,
     byminute = 0,
     cache = True,
-    dtstart=datetime(1970, 1, 1, tzinfo = pytz.utc),
+    dtstart=datetime(2001, 1, 1, tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 
 # Recurrence rules for excluding the market open/close on new years.
@@ -118,7 +119,8 @@ new_years_opens = rrule.rrule(
     byhour = 14,
     byminute = 30,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 new_years_closes = rrule.rrule(
     rrule.MONTHLY,
@@ -126,7 +128,8 @@ new_years_closes = rrule.rrule(
     byhour = 21,
     byminute = 0,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 
 # Recurrence rules for excluding MLK day. It is always the third
@@ -138,7 +141,8 @@ mlk_opens = rrule.rrule(
     byhour = 14, 
     byminute = 30,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 mlk_closes = rrule.rrule(
     rrule.MONTHLY,
@@ -147,7 +151,8 @@ mlk_closes = rrule.rrule(
     byhour = 21, 
     byminute = 0,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 ) 
 
 # Recurrence rules for generating the market open/close for
@@ -160,7 +165,8 @@ presidents_day_opens = rrule.rrule(
     byhour = 14,
     byminute = 30,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 presidents_day_closes = rrule.rrule(
     rrule.MONTHLY, 
@@ -169,7 +175,8 @@ presidents_day_closes = rrule.rrule(
     byhour = 21,
     byminute = 0,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 
 # Recurrence rules for generating the market open/close for good
@@ -181,7 +188,8 @@ good_friday_opens = rrule.rrule(
     byhour = 14,
     byminute = 30,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 good_friday_closes = rrule.rrule(
     rrule.DAILY,
@@ -189,7 +197,8 @@ good_friday_closes = rrule.rrule(
     byhour = 21,
     byminute = 0,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 ) 
 
 # Recurrence rules for generating the market open/close for memorial
@@ -201,7 +210,8 @@ memorial_day_opens = rrule.rrule(
     byhour = 14, 
     byminute = 30,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 memorial_day_closes = rrule.rrule(
     rrule.MONTHLY,
@@ -210,7 +220,8 @@ memorial_day_closes = rrule.rrule(
     byhour = 21, 
     byminute = 0,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 
 # Recurrence rules for generating the market open/close for July 4th.
@@ -221,7 +232,8 @@ july_4th_opens = rrule.rrule(
     byhour = 14,
     byminute = 30,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 july_4th_closes = rrule.rrule(
     rrule.MONTHLY,
@@ -230,7 +242,8 @@ july_4th_closes = rrule.rrule(
     byhour = 21,
     byminute = 0,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 
 # Recurrence rule for generating the market open/close for labor day.
@@ -242,7 +255,8 @@ labor_day_opens = rrule.rrule(
     byhour = 14, 
     byminute = 30,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 labor_day_closes = rrule.rrule(
     rrule.MONTHLY,
@@ -251,7 +265,8 @@ labor_day_closes = rrule.rrule(
     byhour = 21, 
     byminute = 0,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 
 # Recurrence rule for generating the market open/close for
@@ -264,7 +279,8 @@ thanksgiving_opens = rrule.rrule(
     byhour = 14,
     byminute = 30,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 thanksgiving_closes = rrule.rrule(
     rrule.MONTHLY,
@@ -273,7 +289,8 @@ thanksgiving_closes = rrule.rrule(
     byhour = 21,
     byminute = 0,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 
 # Recurrence relation for generating the market open/close for
@@ -286,7 +303,8 @@ christmas_opens = rrule.rrule(
     byhour = 14,
     byminute = 30,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
 christmas_closes = rrule.rrule(
     rrule.MONTHLY,
@@ -295,8 +313,10 @@ christmas_closes = rrule.rrule(
     byhour = 21,
     byminute = 0,
     cache = True,
-    dtstart = datetime(1970, 1,1,tzinfo = pytz.utc)
+    dtstart = datetime(2000, 1,1,tzinfo = pytz.utc),
+    until=datetime(2014, 1, 1, tzinfo = pytz.utc)
 )
+
 # All NYSE observed holidays.
 holiday_opens = [
     new_years_opens,
@@ -322,12 +342,15 @@ holiday_closes = [
 ]
 
 # Valid market opens are given by all market opens minus holidays.
-opens = rrule.rruleset()
+opens = rrule.rruleset(cache=True)
 opens.rrule(market_opens_with_holidays)
 for holiday_rule in holiday_opens:
     opens.exrule(holiday_rule)
+open_count = opens.count()
 
-closes = rrule.rruleset()
+closes = rrule.rruleset(cache=True)
 closes.rrule(market_closes_with_holidays)
 for holiday_rule in holiday_closes:
     closes.exrule(holiday_rule)
+close_count = closes.count()
+