Showing Month Abbreviation With Using 2 Characters

[Kevin@Radstock]

HI
Maybe try incorporating the LOOKUP function.

=LOOKUP(MONTH(A1+180),{1,2,3,4,5,6,7,8,9,10,11,12} ,{"JA","FE","MR","AL","MA","JN","JL","AU","SE","OC ","NO","DE"})

Alternatively the VLOOKUP can be used as well.

[Rick Rothstein]

You can format your cells as General and then put this formula in B1 and copy it down...

=REPLACE(UPPER(TEXT(A1+180,"yyyy/mmm/d")),6,3,CHOOSE(MONTH(A1+180),"JA","FE","MR","AL","MA","JN","JL","AU","SE","OC ","NO","DE"))

Change the two 180's to 270's in the above formula and use it in cell C1.