open source scheduling system for shift workers

[Noah]

Hi there,

Is there a good open source scheduling system that somebody can 
recommendation?  Basically I need to track people who perform duties on 
4 to 8 hour shifts.  I am sure there is something written out there.  I 
have found limitations with phpscheduleit for creating 4 hour slices 
multiple times a day.  Maybe recent improvements to the code has fixed 
this.  But are there other options out there.

Cheers,

Noah