The season of Lent spans 40 weekdays beginning on Ash Wednesday and climaxing during Holy Week with Holy Thursday (Maundy Thursday), Good Friday, and concluding Saturday before Easter.
( http://www.cresourcei.org/cylent.html )
The period of Lent in terms of calendar days changes from year to year. For 2013; the days are
February 13 - Ash Wednesday
March 24 - Palm Sunday
March 28 - Maundy (Holy) Thursday
March 29 - Good Friday
March 31 - Easter Sunday (Western Christianity - Roman Catholic, Anglican Communion, Protestant Churches, etc.)
May 5 - Easter Sunday (Orthodox Christianity - Eastern Orthodox Churches)
( http://christianity.about.com/od/easter/qt/easter2013.htm )
There is difference in dates between Western and Eastern churches
( http://christianity.about.com/od/faqhelpdesk/qt/whyeasterchange.htm )
The period of Lent is to be observed by the persons who want to join the christian faith and it also to be observed of the christian community to accept the new person into the faith. It is used as a period of reflection and repentance for sins committed.