In the Western Christian calendar, Ash Wednesday is the first day of Lent. (Eastern Christianity starts Great Lent on Clean Monday, which, due to differences in the calculation of Easter and the length of Great Lent, is often later in the year.)
It occurs forty days before Easter not counting Sundays (which are not included in Lent); it occurs forty-four days before Good Friday counting Sundays. Its placement varies each year, according to the date of Easter. The date can vary from early February to as late as the second week in March.