Formula for the previous workday before the 15th of the month if it falls on a weekend.

I get paid on the 15th if it's a workday or on the last workday before the 15th if the 15th of the month falls on a weekend. I have a series of data on column a with the days of 15 in consecutive months.
Is there a formula to return, for example for February the 13th of February because it falls on a Friday while the 15th is a Sunday?
I heard of the WORKDAY function but I just can't seem to get it to work.

A
1 15/01/2015
2 15/02/2015
3 15/03/2015
4 15/04/2015

Thanks.

Row\Col	A	B	C
2	Thu 15 Jan 2015	Thu 15 Jan 2015	B2: =WORKDAY(A2+1, -1)
3	Sun 15 Feb 2015	Fri 13 Feb 2015
4	Sun 15 Mar 2015	Fri 13 Mar 2015
5	Wed 15 Apr 2015	Wed 15 Apr 2015

You're welcome.