I have a dataset FiscalDate year Value 01JAN2012 2012 2 14JAN2012 2012 3 15JAN2012 2012 4 04FEB2012 2012 6 05FEB2012 2012 7 01JAN2013 2013 1 12JAN2013 2013 2 08MAR2014 2014 10 09MAR2014 2014 11 If it is the first instance of the year and has a value of 2 than it should be reduced by 1. Here is the output that I need FiscalDate year Value 01JAN2012 2012 1 14JAN2012 2012 2 15JAN2012 2012 3 04FEB2012 2012 5 05FEB2012 2012 6 01JAN2013 2013 1 12JAN2013 2013 2 08MAR2014 2014 10 09MAR2014 2014 11