Pivot Table sort by day

Hi,

This is annoying me now, I have two pivot tables with names, days and times on. Both pivots are sorting by name first correctly, but when it gets to days one is sorted by mon to sun, but the other is Fri, Mon, Sat, Sun, Thu, Tue, Wed!?

The only difference I can see is that the first pivot table had no manipulation to the day, but the second was shrunk in length (as it would say something like Mon 28-Feb-2011)

Any ideas?

Hi
could you post a sample, including source data?