If your field is of the type "Date/Time" then you should be able to configure the display if the data by adjusting the Regional Settings in the Windows Control Panel.
If that's not practical (as it would affect other programs), the you can use the dtoc() function to convert the date to a character string, and then all the useful text functions like extract(), substr(), left() etc should help you get what you need.
Assuming the source field is a date field have you looked at using the MONTH() and YEAR() functions?
A calculated field using the concatenation of those two functions should give what you want .
For a 2 character year rather than 4 character year .....
HOWEVER - if you always want the month to be 2 characters (01 through 12) and a 2 character year to display as "08", "09", etc. you will need to specify that as part of the STR function. It's covered in the Help file so maybe no point in repeating it here at length. It's easy enough to do when you see the examples.
If the date is not a date field you may neet to 'convert' it first using the CtoD() function.
Does this move things forward for you?
If the data format is not a date as recognised by your Regional Settings then the approaches suggested by Olly above are the way to go.