Cumulative count

deleted-user-qpvAI3Fo0MKR

I'm trying to create a cumulative count of IDs by Date in a field called Count.

For example, with these 3 IDs highlighted below, the results of Count would be 1, 2 and 3.

Any help would be greatly appreciated.

*edit - in the screenshot above the IDs have been sorted to be grouped.

DarrenWiens2

See here for the logic behind tracking the count in a dictionary: https://community.esri.com/message/596160?commentID=596160#comment-596160 

And here for Update Cursor (ideally, your data is in a database and you can use ORDER_BY): UpdateCursor—Data Access module | ArcGIS Desktop