Calendar "apps"

[FG1]

I use a HTC Touch2 and being a shift worker I have my shift in my calendar.
We work a pattern that means that it takes 28 days to run a cycle.
One of the lads at work has recently got an I-Phone and is looking for calendar app that will let him enter a shift that has an occurrance of 28 days.
Does anybody know of a decent app with this ability???

[injury_ian]

I use google calender on my iphone, but then I run a not as arkward but not straight forward 8 day cycle.

If there is a pattern to it you can tell it you want x to happen every 28 days and eventually once a,b,c,d.. are all put in you should have a full cycle.