In Google Sheets, I have a spreadsheet called Events/Incidents which staff from various branches populate. I want Column B to automatically generate a unique ID based on the year in column A and the previously populated event. Given that there could be several events on a particular day, rows in column A could have duplicate dates.
The following is an example of what I am looking for in column B:
There can be no duplicates. Would really appreciate some help with either code or formula.

