I doubt this can be done but may as well ask to find out.

I'm currently looking at financial transactions over a 12 month period
and I'm only interested in looking at on a month period and not so
interested in the transaction date. In this financial period there
are actually 13 periods (months) which are...

July, August, n, June and Adjustment Period

Each month, the date is set to the first of each month. EG: 1/6/2008
and is displayed as Jun-08

So the data would sort correctly, I've made the Adjustment Period date
as 30/06/2008

However, seeing Jun-2008 can sometimes be a bit confusing.....

I'm wondering if there's a way to display 30/06/08 as Adj-08 rather
than Jun-08 and still be recognised as a date so that it would sort
correctly if I wanted to go by date order without having to insert any
extra columns to have an IF formula that would be something like (IF
CELL < 30/06/2008 then CELL else ADJ-2008) which I think, might be
the only way.

Any suggestions?