Decrypting algorythm

I am using a tripple des encryption algorythm that encrypts dates. I
dump these encrypted dates to a text file.

Thirty dates in this format:

EncodedDate | Date
fsdgjf = 01/01/2005
daskd = 01/02/2005
jkdfhjf = 01/03/2005
.... continued

What would be the steps to reversing this encryption engineering. To
find the factor.... I want to build a program to test the strength of
my prime.