Palm Sunday marks the beginning of Holy week -  April 17  - 2011

Good Friday - commemorate the death of Jesus  on the Cross - April 22 - 2011

Easter Sunday marks the end of the Holy week -   April 24  - 2011

This is a time of struggle, renunciation and intentional suffering. As it is mentioned in "All and Everything"  by G.I.Gurdjieff,  it is a time to provide shocks to "the Planetary body", by means of abstinence.
This period of the year is an opportunity open to us to acquire the strength necessary to overcome the impulses of our denying forces, by creating conditions of sacrifice and intelligent suffering, like "fasting and prayer.         

Fasting means not eating anything, while abstinence means not eating some things. Fasting is what Muslims do during the Ramadan between sunrise and sunset. The Christian Lent meant in its origins abstinence of all food of animal origin. Ideally there was only one meal a day.

"Traditionally, in its origins Christians abstain from meat consumption during Lent"

"During the six weeks between Carnival and Easter (forty days of the withdrawal into the wilderness of Jesus)  there was an extra prohibition. Not only meat, but also milk, butter, cheese and eggs were banned from the table."  - Lent History / Catholic Source

Now all that is left for very few catholic is Friday as an obligatory  "fish day" In this way one was weekly reminded of Jesus who died on the cross on what we call "Good Friday".

"And even this one surviving food custom is either already fading completely out of the ordinary life of the followers of this religion, or its observance is so changing year by year that no shock is obtained from it for the fasters, though it was just for that shock that this "fast"  was established"
                   "All and Everything" -

How to Calculated the 40 Days of Lent:

Lent is 40 days long, but there are 46 days between Ash Wednesday, and Easter.

This  takes us back to the earliest days of the Church. Christ's original disciples, who were Jewish, grew up with the idea that the Sabbath—the day of worship and of rest—was Saturday, the seventh day of the week, since the account of creation in Genesis says that God rested on the seventh day.

Christ rose from the dead, however, on Sunday, the first day of the week, and the early Christians,  saw Christ's Resurrection as a new creation, and so they transferred the Sabbath from Saturday to Sunday.

Christians were forbidden to fast and do other forms of penance on Sundays. Therefore Sundays could not be included in the count.