Evolution date format question

[Kostas Papadimas <pkst gmx net>]

OK I am confused.. What does the string 
On %a, %Y-%m-%d at %H:%M %%+05d, %%s wrote: stands for In Evolution?

I believe that (please correct me if it is wrong) %a, means Weekday (e.g
Monday),and %Y-%m-%d means y/m/d (e.g 2004/01/19). %H:%M means
Hour/Minute, But I have no idea what %%+05d means...
Also its is Ok to change the %Y-%m-%d format to %d-%m-%Y ?

TIA
Kostas