DatePart(interval,date) For quarters, the interval will equal "q". This is based on the calendar year. It will return a number: 1, 2, 3 or 4. Intervals also include weeks, "ww", which returns a number from 1 to 52.
Example: YourDate is 1/23/03. DatePart("q",YourDate) will return 1 for 1st quarter.
If your using a fiscal year, calculate what week YourDate is in, then assign it to the fiscal quarter.