Picking up on that theme, one could use the DAYS360 function and divide by 30
for a standardized way of handling the variation in month lengths.

On Fri, 4 Feb 2005 16:51:55 -0800, "RagDyer" wrote:

BTW,
Jan.1 to Jun.15 is only 5.5 months, isn't it?

One approach might be to calculate 30 day months, where,
A1 = start - 1/1/05
B1 = end - 6/15/05

Format C1 as General or Number, and enter:

=(B1-A1)/30