I am entering a start time and an end time for hours minutes and seconds, formatted Custom 0|:00|:00, so that when I simply type 75200, it displays as 07:52:00. These are columns A and B. Columns C and D are supposed to convert these times to a number so that Column E will display the total hours, minutes, and seconds elapsed on each row. It appears to work, as you can see on the attached (see formulas used on Sheet 1 and results on Sheet 2), but it does not calculate correctly when I go from the hour of 7:58 to the hour of 8:01, and it also does not calculate correctly when I go over an hour or time elapsed, as shown from 8:14 to 9:18. The problem may stem from incorrect functions in Columns C and D, or it may be a problem with the formatting of Column A, or a combination of issues. I can't see why the formulas work some times, but not always.