I recieve income on the 1st and the 15th of every month, regardless of
the month, or day.

Understanding the serial number feature of Excel, I cannot create a
autofill that will fill in the 1st and 15th of every month.

I need to be able to type in the 1st of a month then autofill across
and have it pick up the 1st and 15th of every month.

How can this be performed?