Calculate number of occurences with last 3 and 6 months

Hi,

I have a row containing:

Date entered
Name
Date of Birth (DOB)
Occurrences of Name + DOB this Month
Occurrences of Name + DOB within last 3 Months
Occurrences of Name + DOB within last 6 Months

I can manage the occurrences this month but haven't a clue how to calculate the 3 and 6 months ones. I have attached a sheet and would appreciate some guidance and help.

Thank you in advance.