Why is it called Ascension Day?

Ascension Day is called so because it commemorates the ascension of Jesus Christ into heaven. The term "ascension" refers to the act of rising or being lifted up. According to Christian belief, after his resurrection, Jesus spent 40 days on Earth appearing to his disciples and teaching them about the kingdom of God. On the 40th day, he ascended into heaven, being lifted up from the Mount of Olives in the presence of his disciples.