This year Easter will be celebrated on March 31, but in 2014 it will occur on April 20. The reason has to do with the mismatch between the periodicity of the sun and the moon and the long history of human efforts to create a reliable and consistent calendar.
I don't want to knock those who give stuff up. In fact, I understand the significance of self-denial, but if we're not careful, we can so easily just fall into religious practice for the sake of religious practice.
Lent is a call to weep for what we could have been and are not. Lent is not about penance. Lent is about becoming, doing and changing whatever it is that is blocking the fullness of life in us right now.
Since ancient times, Christians have used the Christian calendar (also called the liturgical year) to orient themselves to the two most significant seasons in the yearly Christian cycle of time: Christmas and Easter.