Absence Quota

Hi Experts

I am learning SAP HCM, I created an absence quota and run the program RPTQTA00 and it has generated the entitlement.When I try to book absence under PA30, I get a message like->No data stored for absences in the selected period. I have changed different periods but same msg .

Do I have to run any time schema before booking absences? please help me.

Thanks

Anjaan