Forgiveness Sunday
Today is the last day of [an article such as "the" or "an" should go here] Orthodox holiday carnival called Maslenitsa, also known as Butter Week. Everybody askes each other for forgiveness and everybody traditionally replies: "God will forgive and I forgive". Tomorrow starts [you could say "Tomorrow is the start of" or "Tomorrow is the beginning of"] Great Lent which lasts for 40 days from Clean Monday until the Friday of the Sixth Week.

Thanks for sharing this! I like to hear about holidays in other countries.