What is the rule to determine the first date?

For months that starts on a Friday what does it do? Which one should it take? E.g.:
1st April 2016
8th April 2016
15th April 2016
22nd April 2016
29th April 2016

Let's say you took 8th and 22nd April, 14 days from 22nd April is actually 6th May, but that's the first Friday of May, how should the macro decide to use 13th May? Is it always second Friday of the month? Followed by fourth Friday?

Then, what do you want the macro to do after finding the correct dates?