>If you are truly calculating financial time spans (to calculate accrued interest on such things as fixed income securities (bonds, etc.), there are VERY exact definitions of how do to that.

This is exactly what I am doing. I just need to find the standards.

> You literally must do it by counting an exact number of days - in some cases, the accrued interest on two consecutive days can be the same value. There were some bonds that counted on a 360-day year, and others that counted on a 365-day year. All very confusing.

Well, there are different ways of doing it from what I understand, and I need to do it using an "actual/actual" method, and a "30/360" method. I believe the first is an exact count of the number of days and the second assumes 30 day months and 360 day years for fractional years. I will check out NASD and SEC to see what I can turn up. Thanks.