Default calendar changed but made no impact

Dear fellow professionals,

I'm havign to use ms project 2003 to plan for a very small job, but with resource and number of hours (in work).

The actual working hours for all resources are 8-12, 13-16:30, so 7.5 hours per day and 37.5 hours per week. Straight forward. I therefore set this as default in the calendar, but when I go to the calendar itself the defalut for each day is still 8 hours, but when I check in Tools-Options-Calendar the default is as I set it to be. If I open "Change Working Time" all the default working days are still showing 8 hours per day, but when I click on options it shows my setting!

The result of this is that the software assumes there is 8 hours in a day, so 37.5 hours of work takes 4 and half days.

Can someone plase help?

thanks a lot

wei