VLOOKUP date issue (formatting?)

Okay my accounting software returns the date, 12/30/2013, as 123013 when I export to excel. When I go in and change it to date format it goes to 2/16/2229? I'm trying to vlookup that 123013 to a table of dates to return the correct month in my accounting period but I can't seem to get it. I tried to change the table to the 123013 type format but it doesn't work. It doesn't say N/A but it returns Mar-14 (30114 to 33114 in the table)....Which obviously isn't what I'm looking for. Is there any way I can convert the data so this thing will match up? Hopefully I explained this in a way that makes sense!

The formula I am using is: =VLOOKUP(O10,Calendar!$G$5:$I$28,3) where G is the beginning of the period, H is the end, and I is the "Mar-14" type style I want it to show. This formula has worked for my other files, but only the ones using the 12/30/2013 formatting.

Any help is appreciated!