In 2004, Ash Wednesday falls on February 25. Its placement varies each year, according to the date of Easter.

Some Christians treat Ash Wednesday as a day for remembering one's mortality. Masses are traditionally held on this day at which attendees are blessed with ashes by the priest ministering the ceremony. The minister marks the forehead of each celebrant with black ashes, leaving a mark that the worshipper traditionally leaves on his or her forehead until sundown, before washing it off. This symbolism recalls the ancient oriental tradition of throwing ash over one's head signifying repentance before God (as related numerous times in the Bible). In Roman Catholicism, it is a day of fasting and abstinence.

Being the first day of Lent, it comes the day after Shrove Tuesday. In certain parts of the UK, Ash Wednesday similarly involves the ritual consumption of a food stuff; in this case the homonymous dish hash.

Ash Wednesday is also the title of a poem by T. S. Eliot.