diff --git a/Pipfile b/Pipfile
index f115954..33346a0 100644
--- a/Pipfile
+++ b/Pipfile
@@ -15,4 +15,4 @@ pytz = "*"
 pylint = "*"
 
 [requires]
-python_version = "3.5"
+python_version = "3.6"
diff --git a/Pipfile.lock b/Pipfile.lock
index d7939a9..e973df1 100644
--- a/Pipfile.lock
+++ b/Pipfile.lock
@@ -1,11 +1,11 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "c71cc3fb1c386033f20ceadbde8da577f6af6c645333056a5e84bff225fe936d"
+            "sha256": "ffdcc7d81db0f5c5be8a6c0e7f3d57a38eff7d66c904d23adfc53ba06e7af315"
         },
         "pipfile-spec": 6,
         "requires": {
-            "python_version": "3.5"
+            "python_version": "3.6"
         },
         "sources": [
             {
diff --git a/main.py b/main.py
index ca484d0..a3b4a53 100644
--- a/main.py
+++ b/main.py
@@ -6,19 +6,10 @@ from httplib2 import Http
 from oauth2client import file, client, tools
 import pytz
 
+# We don't store this url in the source, as it is sensitive
 URL = open("timetableurl").read().strip()
 
-def parse_events(page_data):
-    soup = BeautifulSoup(page_data, features="html.parser")
-
-    source = ""
-    for script in soup.head.findAll("script", {"type": "text/javascript"}):
-        if not script.has_attr("src"):
-            source = script.text
-            break
-    
-    events_data = source.split("events:")[1].split("]")[0] +"]"
-
+def parse_events(events_data):
     # Replace date objects with tuples, easier to parse
     events_data = events_data.replace("new Date", "")
 
@@ -37,6 +28,7 @@ def parse_events(page_data):
  
         cleaned_data += line + "\n"   
 
+    # Parse the event, as if it were a dict
     parsed_data = eval(cleaned_data)
 
     # Parse the datetime info
@@ -57,8 +49,22 @@ def parse_events(page_data):
 
     return parsed_data
 
-def get_timetable_data(url):
-    return requests.get(url).text
+
+def get_events_data(url):
+    page_data = requests.get(url).text
+
+    soup = BeautifulSoup(page_data, features="html.parser")
+
+    source = ""
+    for script in soup.head.findAll("script", {"type": "text/javascript"}):
+        if not script.has_attr("src"):
+            source = script.text
+            break
+    
+    events_data = source.split("events:")[1].split("]")[0] +"]"
+
+    return events_data
+
 
 def create_google_event(event):
     new_event = event.copy()
@@ -77,30 +83,68 @@ def create_google_event(event):
                               'overrides': [{'method': 'popup', 'minutes': 30}]}
     return new_event
 
-# If modifying these scopes, delete the file token.json.
-SCOPES = 'https://www.googleapis.com/auth/calendar'
 
-def main():
-    """Shows basic usage of the Google Calendar API.
-    Prints the start and name of the next 10 events on the user's calendar.
-    """
+# Read and write access
+SCOPES = "https://www.googleapis.com/auth/calendar"
 
-    type_to_color = {}
-    color_queue = list(range(0, 12))
-    
-    store = file.Storage('token.json')
+def get_calendar_service():
+    '''
+    Connect to the google calendar service, and return the
+    service object
+    '''
+
+    store = file.Storage("token.json")
     creds = store.get()
 
+    # Run prompt to get the google credentials
     if not creds or creds.invalid:
-        flow = client.flow_from_clientsecrets('credentials.json', SCOPES)
+        flow = client.flow_from_clientsecrets("redentials.json", SCOPES)
         creds = tools.run_flow(flow, store)
-    service = build('calendar', 'v3', http=creds.authorize(Http()))
 
-    cov_events = parse_events(get_timetable_data(URL))
+    return build("calendar", "v3", http=creds.authorize(Http()))
+
+
+def execute_batch(service, commands):
+    batch = service.new_batch_http_request()
+    batch_count = 0
+
+    for command in commands:
+        batch.add(command)
+        batch_count += 1
+        
+        if batch_count > 999:
+            batch.execute()
+
+            batch = service.new_batch_http_request()
+            batch_count = 0
+    
+    if batch_count > 0:
+        batch.execute()
+
+
+def main():
+    type_to_color = {}
+    # A queue of colors, where a color is removed when
+    # when an event we have not seen before exists
+    color_queue = list(range(0, 12, 3))
+
+    service = get_calendar_service()
+
+    # Get a list of all events in the future
+    results = service.events().list(timeMin=datetime.now().isoformat() + 'Z', calendarId='primary').execute()
+    future_events = results.get("items", [])
+
+    cov_events = parse_events(get_events_data(URL))
+    new_events = []
+
+    new_summaries = set()
 
     for event in cov_events:
+        if not event:
+            continue
+
         new_event = create_google_event(event)
-        
+
         color_type = new_event["mainColor"]
         
         if color_type in type_to_color:
@@ -112,6 +156,33 @@ def main():
 
         new_event["colorId"] = colorId
 
-        service.events().insert(body=new_event, calendarId='primary').execute()
+        new_events.append(new_event)  
+        new_summaries.add(new_event["summary"])  
 
-main()
+    # Make sure we remove old events so as not to create duplicates
+    if not future_events:
+        print('No existing events found')
+    else:
+        deletes = []
+        for existing_event in future_events:
+            if "summary" in existing_event and existing_event["summary"] in new_summaries:
+                deletes.append(service.events()
+                                      .delete(calendarId='primary', 
+                                              eventId=existing_event['id']))
+
+
+        print(f'Removing {len(deletes)} existing events')
+        execute_batch(service, deletes)
+
+    inserts = []
+    for new_event in new_events:
+        inserts.append(service.events()
+                              .insert(body=new_event, 
+                                      calendarId='primary'))
+    print(f"Inserting {len(inserts)} new events")
+    execute_batch(service, inserts)
+                    
+
+
+if __name__ == "__main__":
+    main()