I am tracking Time To Failure (TTF) over a period of a week in Excel 2000. I am having problems getting excel to keep the format to HH:MM format when the TTF is greater than 1 day. For example: a TTF= 25:42 (25 hours and 42 minutes) is being returned as 1:42. My data columns are start date, start time, failure date, failure time, and TTF (HH:MM).
