deleting file based on date which is on the Filename Useing powershell

i am doing a project and deadline is coming too close .......

this is how file in my folder looks BRDB0001_db_F20130316132517.bak

i hve to delet file based on date on its file name which is older than 3 days from now BRDB001_DB_F is same for all files

2013 is year

o3 is month

16 is date and remaining is time

so how can i delet file based on date on it file name

thanks in advance

tshering tashi