"Lucy N" wrote in message
...
Whilst working all my dates have started to show up as their serial
values. I
tried to change the format back but it won't work. Can anyone help?

What format are the cells currently?

Are you sure that you've got numbers in there, rather than text? [If you
change the number of figures after the decimal point in Number format, does
this change show up in the cells? If not, then you may need to do a Paste
Special trick like adding zero or multiplying by 1 to convert from text to
number, and then you should be able to format cells as date.]
--
David Biddulph