How to check if a year in a cell is a leap year

Hey! I am new and would really appreciate help with this. I need a formula that can calculate the following:

If (cell B1 (2014)) is leap year AND (cell D145=28) (cell F145=D145+1) value if false (cell F145="")

I was basically trying to make the days auto populate once the days for the first week of the month were inputted. What I would prefer, is to have all the days auto populate based on the current year in cell B1. I attached two worksheet months as reference. If anyone knows a better way, I'm all for it. Thank you.