The first day of Lent — 40 days of penitence before Easter.
Ash Wednesday marks the start of the 40-day Lenten season of fasting, prayer, and repentance leading to Easter. The name comes from the practice of marking foreheads with ashes — typically burned palm fronds from the previous year's Palm Sunday — as a sign of mortality and penitence.
Computed for Xi'an (Asia/Shanghai) using local sunrise, sunset and astronomical positions.