Christians will begin marking Wednesday the lead up to Easter, the holiest day on the Christian calendar, with the start of Lent. The solemn religious observance traditionally involves believers engaging in prayer and penance to remember the sacrifice of Jesus. Below are some key facts to know about the holiday.

What Is Ash Wednesday? While the start of Lent season varies each year due to Easter Sunday being decided by the lunisolar calendar, it always begins in either February or March, 46 days before Easter, with Ash Wednesday. The day signals the time of penance, with Christians across the world attending church services where the pastor or priest will draw ashes on their foreheads in the shape of a cross. The ashes symbolize the dust from which God made people. As he applies the ash, a pastor or priest will say words from Genesis 3:19: “For dust you are and to dust you shall return.”

Why Does It Last 40 Days? The season of Lent commemorates Jesus’ time in the Judean desert spent fasting and battling the temptations of Satan, as told in the gospels of Matthew, Mark and Luke. Like the fast of Moses detailed in the Book of Exodus, it is believed to have lasted 40 days. However, eagle-eyed readers will have spotted that Lent actually lasts 46 days. That’s because Sundays are not counted.

Why Do People Give Up Things? Lent is a time of penance in commemoration of Jesus’ sacrifice in the desert. For Christians, that sacrifice often takes the form of giving up certain foods or vices such as smoking or alcohol. Another of the most common things to sacrifice is chocolate. Some of the more dedicated believers will fast daily for the entire 40 days, in a ritual similar to that observed by Muslims during Ramadan. Others may choose to use the time to volunteer.