diff --git a/tests/test_perf_tracking.py b/tests/test_perf_tracking.py
index e2ae3a4d..659e9677 100644
--- a/tests/test_perf_tracking.py
+++ b/tests/test_perf_tracking.py
@@ -41,8 +41,8 @@ oneday = datetime.timedelta(days=1)
 tradingday = datetime.timedelta(hours=6, minutes=30)
 
 
-def create_txn(sid, price, amount, dt):
-    return create_transaction(sid, amount, price, dt, "fakeuid")
+def create_txn(event, price, amount):
+    return create_transaction(event, amount, price, "fakeuid")
 
 
 def benchmark_events_in_range(sim_params):
@@ -130,7 +130,7 @@ class TestDividendPerformance(unittest.TestCase):
             events[2].dt
         )
 
-        txn = create_txn(1, 10.0, 100, events[0].dt)
+        txn = create_txn(events[0], 10.0, 100)
         events.insert(0, txn)
         events.insert(1, dividend)
         results = calculate_results(self, events)
@@ -169,7 +169,7 @@ class TestDividendPerformance(unittest.TestCase):
         )
 
         events.insert(1, dividend)
-        txn = create_txn(1, 10.0, 100, events[3].dt)
+        txn = create_txn(events[3], 10.0, 100)
         events.insert(4, txn)
         results = calculate_results(self, events)
 
@@ -203,9 +203,9 @@ class TestDividendPerformance(unittest.TestCase):
             events[3].dt
         )
 
-        buy_txn = create_txn(1, 10.0, 100, events[0].dt)
+        buy_txn = create_txn(events[0], 10.0, 100)
         events.insert(1, buy_txn)
-        sell_txn = create_txn(1, 10.0, -100, events[3].dt)
+        sell_txn = create_txn(events[3], 10.0, -100)
         events.insert(4, sell_txn)
         events.insert(0, dividend)
         results = calculate_results(self, events)
@@ -240,9 +240,9 @@ class TestDividendPerformance(unittest.TestCase):
             events[5].dt
         )
 
-        buy_txn = create_txn(1, 10.0, 100, events[1].dt)
+        buy_txn = create_txn(events[1], 10.0, 100)
         events.insert(1, buy_txn)
-        sell_txn = create_txn(1, 10.0, -100, events[3].dt)
+        sell_txn = create_txn(events[3], 10.0, -100)
         events.insert(3, sell_txn)
         events.insert(1, dividend)
         results = calculate_results(self, events)
@@ -281,7 +281,7 @@ class TestDividendPerformance(unittest.TestCase):
             pay_date
         )
 
-        buy_txn = create_txn(1, 10.0, 100, events[1].dt)
+        buy_txn = create_txn(events[1], 10.0, 100)
         events.insert(2, buy_txn)
         events.insert(1, dividend)
         results = calculate_results(self, events)
@@ -321,7 +321,7 @@ class TestDividendPerformance(unittest.TestCase):
             events[3].dt
         )
 
-        txn = create_txn(1, 10.0, -100, events[1].dt)
+        txn = create_txn(events[1], 10.0, -100)
         events.insert(1, txn)
         events.insert(0, dividend)
         results = calculate_results(self, events)
@@ -411,7 +411,7 @@ class TestPositionPerformance(unittest.TestCase):
             self.sim_params
         )
 
-        txn = create_txn(1, 10.0, 100, self.dt + onesec)
+        txn = create_txn(trades[1], 10.0, 100)
         pp = perf.PerformancePeriod(1000.0)
 
         pp.execute_transaction(txn)
@@ -482,7 +482,7 @@ single short-sale transaction"""
 
         trades_1 = trades[:-2]
 
-        txn = create_txn(1, 10.0, -100, self.dt + onesec)
+        txn = create_txn(trades[1], 10.0, -100)
         pp = perf.PerformancePeriod(1000.0)
 
         pp.execute_transaction(txn)
@@ -671,13 +671,12 @@ trade after cover"""
         )
 
         short_txn = create_txn(
-            1,
+            trades[1],
             10.0,
             -100,
-            self.dt + onesec
         )
 
-        cover_txn = create_txn(1, 7.0, 100, self.dt + onesec * 6)
+        cover_txn = create_txn(trades[6], 7.0, 100)
         pp = perf.PerformancePeriod(1000.0)
 
         pp.execute_transaction(short_txn)
@@ -785,18 +784,17 @@ shares in position"
             400
         )
 
-        saleTxn = create_txn(
-            1,
-            10.0,
-            -100,
-            self.dt + onesec * 4)
-
         down_tick = factory.create_trade(
             1,
             10.0,
             100,
             trades[-1].dt + onesec)
 
+        saleTxn = create_txn(
+            down_tick,
+            10.0,
+            -100)
+
         pp.rollover()
 
         pp.execute_transaction(saleTxn)
diff --git a/zipline/finance/slippage.py b/zipline/finance/slippage.py
index b93b64f6..f8ed0f13 100644
--- a/zipline/finance/slippage.py
+++ b/zipline/finance/slippage.py
@@ -14,7 +14,6 @@
 # limitations under the License.
 import abc
 
-import pytz
 import math
 
 from copy import copy
@@ -100,12 +99,12 @@ class Transaction(object):
         return py
 
 
-def create_transaction(sid, amount, price, dt, order_id):
+def create_transaction(event, amount, price, order_id):
 
     txn = {
-        'sid': sid,
+        'sid': event.sid,
         'amount': int(amount),
-        'dt': dt,
+        'dt': event.dt,
         'price': price,
         'order_id': order_id
     }
@@ -146,7 +145,6 @@ class VolumeShareSlippage(SlippageModel):
 
     def simulate(self, event, current_orders):
 
-        dt = event.dt
         simulated_impact = 0.0
         max_volume = self.volume_limit * event.volume
         total_volume = 0
@@ -190,12 +188,11 @@ class VolumeShareSlippage(SlippageModel):
 
             if order.direction * cur_amount > 0:
                 txn = create_transaction(
-                    event.sid,
+                    event,
                     cur_amount,
                     # In the future, we may want to change the next line
                     # for limit pricing
                     event.price + simulated_impact,
-                    dt.replace(tzinfo=pytz.utc),
                     order.id
                 )
 
@@ -230,10 +227,9 @@ class FixedSlippage(SlippageModel):
                 return txns
 
             txn = create_transaction(
-                event.sid,
+                event,
                 order.amount,
                 event.price + (self.spread / 2.0 * order.direction),
-                event.dt.replace(tzinfo=pytz.utc),
                 order.id
             )