Need Help With Formula To Calculate Number Of Days

I'm trying to find a formula to give the number of days from January 1 to the day before the date inserted in a cell.

Example: date inserted in cell, 3/31/05
total number of days would be 89 (day before)

Any ideas?

Thank you Richardeye and Duane.

Is there a way to make the formula change the year automatically based on the year in the date instead of a manual change?

Example: if the date was 3/31/06 (C1), change the formula automaticaly from

=C1-DATE(2005,1,1)
To read

=C1-DATE(2006,1,1)

C1= DATE CELL

=a1-DATEVALUE("1/1/05")

with a1 being the cell with your date in it