How They Are Similar:
- Both are periods of reflection around the time of the Passover and Resurrection.
- Both involve a form of fasting or giving up a specific portion of the normal diet.
- Each are bookended by specific observances.
How They Differ:
- Lent involves choosing your own vice to give up. Sometimes this is not even dietary though a specific food vice is usually encouraged. Children (and some adults) commonly give up items they hate or don't consume often. Unleavens involves giving up and completely removing from your premises all products made with leavening. There is no personal choice involved.
- Lent runs for 40 days (give or take depending on the group observing it). Unleavens runs for 7 days.
- Lent is preceded by an episode of excess or gluttony in anticipation of the period. Unleavens is preceded by Passover which is a separate day of reflection and memorial.
- Lent usually ends (again, depends on the group) around Palm Sunday or Crucifixion week. Unleavens begins and ends with a day of solemn assembly.
- Lent is based on the concept of commemorating the 40 day fast observed by Jesus. There is no scriptural command for its observance. Unleavens is specifically commanded in Exodus 12 and Leviticus 23 and the removal of leavening is a symbol of removing sin from our lives (I Corinthians 5:6-8) as well as the consuming of unleavened bread taking on sincerity and truth in addition to it representing the Messiah's body.
So while Lent and Unleavens are diverse from each other, one is no less odd than another (except that one involves actual obedience to commandments given).