Ash Wednesday can fall as early as February 4 and as late as March 10. This is because Ash Wednesday is 46 days before Easter (40 fasting days plus 6 Sundays), and Easter's date varies based on the vernal equinox and full moon. The calculation is: earliest Easter (March 22) minus 46 days = February 4; latest Easter (April 25) minus 46 days = March 10.