The trick for this is that you have to realize that time in Access or Excel doesn't exist as a data type, only as a reformatting of another number type.
In Access, time is a reformatted DOUBLE (floating-point or real) number. In Excel, anything that isn't text or a linked/embedded object is a number. You run into a couple of nasties that make your life trickier, but there is some hope. In general, the concept is that time is treated as a number of days and fractions thereof since a reference date.
First nasty: Access and Excel don't use the same reference date.
If you are doing elapsed-time computations, taking the difference between two times in the internal (DOUBLE) format works just fine. The problem occurs not when you do time diddling and manipulation, but rather when you try to reformat the time.
Second nasty: If you are doing differences between two times, both must be derived from Excel or both must be from Access because...
Third nasty: If at any point you have converted one of those "binary" times from Excel to text and later convert it back under Access, you implicitly changed the reference date.
Now, for Access versions at/after 2007, I believe there is a time format hhh:nn:ss that lets you specify a number of hours beyond 23. However, to really manipulate times that would have a days:hours:minutes:seconds format, you might need to "roll your own" function to do the formatting. I don't know if Excel at/after 2007 supports that same specification.
In summary, the trick is to keep the dates numeric as long as possible and only convert to dates when you absolutely have to do so.
