Hi Norman,
Thanks for the detail on this issue. When you said YEARFRAC produces erros I misinterpreted that to mean it returned an error message, not incorrect results.

After reading your first post I played around with it a little and found that a 10 day span had a different year fraction if it crossed over feb 29, even though both ends were still in the same year. Now I see that YEARFRAC uses your logic in that it considers the year to be from the start date to the same date in the next year.

I also tried a 14 year period starting 1/1/1990 and found that I had to be exactly 3 days short to get a YEARFRAC of exactly 14. It seemed to be using a 365 day year for all years even though I used a basis of 1.

I filed the formula and macro from you and Myrna for future use.

Thanks again,
Mark Graesser