correct week display for sundays

[blush] needed to correct WEEK display for all Sundays (not just on Sun 1st). It did not result on an event-date mismatch, but did cause the week display on Sundays to not display the current week but the one after.
Tested Sun-first and Mon-first WEEK display against the following dates: Sun 1,8,29 jun, Sun 2,30 Jul, Mon 2,30 Jun and Tue 1st Jul. Really think I've nailed it this time ;-)