Hi: DATEDIFF doesn’t give you the difference between the calendar days - it gives you the number of days between the two date-time values.
https://support.workfront.com/hc/en-us/articles/217196767-Understanding-Calculated-Data-Expressions If the first date is “2017-01-01 16:00:00” and the second date is “2017-01-02 08:00:00” it will factor into consideration the times. In order to get the true calendar date difference, without consideration of the time associated with each time entry, you need to use CLEARTIME. Unfortunately, we haven’t been able to get CLEARTIME to work in the past seven months. I’ve had a ticket (1017069) open for seven months on this. If anyone knows how to clear the time off a date, without using CLEARTIME, I’d be indebted to also know. If you only want to count week days, don’t use DATEDIFF, use WEEKDAYDIFF (see help link above). It returns the number of week days between two dates taking into account the date and time associated with each date in the expression. If you don’t want it to factor in the time associated with each date, you’re back to the CLEARTIME issue. Thanks! Eric