Calculation of days of service in the month

[nerio]

If anyone can help me.
I have a recruitment period (from to) and I need to calculate the days of employment in the reference month. For example:
How many days of hiring in March?
Hired on March 10th to April 10th = dd. 22
Hired on February 10th until March 10th = dd. 10
Hired on February 10th to April 10th = dd. 31
Obviously the calculation should be made with a variable based on the chosen month.
Thanks for those who want to give me an indication.

 

[lousyfool]

That's generic PHP (or JS?), not Fabrik.
Sorry, but there are better places on the web for this, like https://stackoverflow.com and others.