...do you mean the format or the actual data?
..incidentally this is yeat another good reason not to store dates as text... store 'em in the natural datatype which is date/time
assuming you want to change the data Id try an update query
set <mydatecolumn> = "2007" & right(<mydatecolumn>, strlen(<mydatecolumn>-4))
where <mydatecolumn> like "2008*";
effectively that query reads
update the specified column (<mydatecolumn>) to....
2007 and append the reaminder of the existing datecolumn.
the reason for the right(<mydatecolumn>, strlen(<mydatecolumn>)-4)
is to cater for the possibility that the date might not be 8 characters.
the strlen returns the number of characters in the datecolumn, the right bit
. the reason we subtract 4 is that we are using the first 4 characters for the year so we don't want these to repeat.
note this will not update any date values which are using 2 digit years unless you have some records for July 2000...
however Id want to do that on a local copy of the data at first top check the query is correct...... and I haven't tested the query
once I was happy that the query was updating the records I wanted and only those then I'd be happy to run it against the remote data.... but be very very careful, just in case you screw the data.