Calculating days between two Dates

Anyone one of you can think of a clever algorithm?

The date input format should be ( dd, mm, yyyy ). All I can think of is that to work out the number of months between the two date. And then work out the number of days for each month, And lastly add up all the days. But this is a pain in the s.

Since leap year is taken into concern, the calculation is quite tedious (although not impossible). I am thinking of the possiblity of a shorter algorithm. It nice if you guys have some suggestions.

Thanks a lot.