assuming that if the start date in the 15th only the second period would be
used and if the 15th was the last day no periods for that month would be
counted.
if there are two cells with Start-date and End-Date
try
= (year(End-Date)-Year(Start-date))*24+(month(Start-date)-month(End
Date))*2+if(day(start-date)<16,0,-1)+if(day(end-date)15,0,-1)

"sforr" wrote:

I need to calculate the number of semi-monthly pay periods between 2 dates,
with the pay periods being the 15th of the month and the last day of the
month. I only want complete periods. Any ideas?