Sometimes there are things that we just do or see and we just move on from without much thought other than maybe a shrug of the shoulders. The names of the Sundays in Lent might be one of those things. Let me explain.
During Advent, we have the 1st through 4th Sundays of Advent. These Sundays are a part of Advent and so we say, “of.”
During Lent, we have the 1st through 5th Sundays in Lent. This is a subtle difference with simply indicates that the Sunday is not a part of Lent. It is in Lent, but it is not of Lent. That is because Lent consists of the 40 days before Easter other than the Sundays. The Sundays are a sort of “Little Easter.”
In fact, we could say everyday is a Little Easter because every day, Jesus is risen. Every day, The Good News of the resurrection of Christ goes forth through His people. Every day is a day when Christians put to death their sin by confessing their sin and Christians rise again to newness of life because Jesus has conquered sin, death, and the devil. God be praised!