Excel formula to calculate intersected dates?

Question

I searched through internet and came up with nothing. I have two tables. one includes work dates and the other has vacation dates. I have to find the intersected dates.

Let me give an example;

1|  A    |      B             |       C          |          D
2|Person |    Work Start Date | work finish Date |Intersected Vacations
3|Mike   |         01.08.2013 |       10.08.2013 |1  (Needed to find)
4|John   |         16.08.2013 |       25.10.2013 |3  (Needed to find)

1|A      |B                   |C
2|Person |Vacation Start Date |Vacation End Date
3|Mike   |         05.08.2013 |       05.08.2013
4|John   |         20.09.2013 |       21.09.2013
5|John   |         01.10.2013 |       01.10.2013

So, I need an excel formula to calculate the vacations between the work days.

Answer 1

Assuming you are counting all days within the periods, including Saturdays and Sundays you can use this "array formula" as per my screenshot below:

Formula is as follows in D3:

=SUM(IF(A$8:A$10=A3,IF(C$8:C$10>=B3,IF(B$8:B$10<=C3,IF(C$8:C$10>C3,C3,C$8:C$10)-IF(B$8:B$10<B3,B3,B$8:B$10)+1))))

confirmed with CTRL + SHIFT + ENTER and copied down to D4

This may look like overkill for your small example but I'm assuming your real data is larger - this solution can be extended as required, even for multiple unsorted vacation periods