Salemaker & specials not working

I am trying to do my first sale and when I key in the details and click insert, it shows the end date as 11/31/2036 rather than the end of July. Both in the Salemaker and Specials it comes up disabled and won't allow me to enable. I have been reading the threads and have reset ALL products master categories id and updated all products sort price order in Tools - Store Manager as suggested, but this has had no effect.
The only other thing I can think of is that I have changed some date formats to dd/mm/yy
Any suggestions would be appreciated!

All fixed. Would you believe I had to key the dates in manually rather than using the calendar!

What version of Zen Cart?

Clean install or an Upgrade?

It is the latest version and not an upgrade.

I cannot reproduce this error ...

I think it may be related to the method you are using on the entry of the dates ... or perhaps a change you may have made to your dates ...

The date does need to be added as: mm/dd/yyyy

Do you recall what types of changes you have made in regard to the dates?