13Jul/10Off
Filtering SharePoint list items by financial quarter
Where the financial year runs from 1st Dec and the list has Q1, Q2, Q3, Q4 in a field called Qtrly Reporting Qtr & the tear in a field called Qtrly Reporting Year
Created to new calculated fields displaying the dates each quarter starts and ends and then filter against [Today]
=IF([Qtrly Reporting Qtr]= "Q1",DATE([Qtrly Reporting Year],03,01),IF([Qtrly Reporting Qtr]= "Q2",DATE([Qtrly Reporting Year],06,01),IF([Qtrly Reporting Qtr]= "Q3",DATE([Qtrly Reporting Year],09,01),IF([Qtrly Reporting Qtr]= "Q4",DATE([Qtrly Reporting Year]-1,12,01),DATE(2000,01,01)))))

With reference too
http://msdn.microsoft.com/en-us/library/bb862071.aspx
http://blog.pentalogic.net/2008/10/advanced-sharepoint-view-and-filters/