Calculating Total Sickness in a rolling 12 month Period

Hi

Wonder if someone can help with my issue please.
I have a spreadsheet that contains about 2 years worth of data, and i want to calculate the total sickness in a rolling 12 month period for each employee different employee within the sheet.
All the different employees and their dates off during those years are in the same spreadsheet. Is there any way i can get this please, for each individual employee as well as the trigger for each person if it applies please.

1. total days off for rolling 12 months
2. Trigger for different absences

I have attached an example sheet, tab1 is the triggers and tab 2 is the data.
Any help will be much appreciated. Thank you

Thanks