Differance Networkdays vs Workdays

Hi

Networkdays calculates how many day are between two dates
Workdays calculates the end date from the start date by the amount of days specified

However they seam to calculate differently

if you do =networkdays(A1,A2) where A1 is 14/09/2015 and A2 is 17/09/2015 it returns 4 days (seams correct)

Then do = workdays(A1,4) it gives the date as the 18/09/2015 not the 17th as you would expect

Doesn't matter the exact date you use the result is the same ie they are one day out to each other.

I'm guessing one counts today and the other doesn't but that really shouldn't happen should it?

Anyone know why?