Yom Kippur, which is the Day of Atonement in the Jewish calendar, lasts only for 25 hours. Yom Kippur is considered to be the most important holiday in the Jewish calendar, and it is observed by Jewish people. They believe that God judges over their past mistakes and decides on what becomes of their destiny on the tenth day after Rosh Hashanah. So, they spend the whole 25 hours praying and fasting.
Other things they are expected to be doing is to be reflecting on their past mistakes, making a decision in their hearts to mend their ways. People do all sorts of good things on this day. They believe that when God sees their heart cry for repentance, God is going to be lenient on them in his judgment. Fasting is very important on Yom Kippur because it will help to cleanse the spirit, soul, and body and remove every evil thing.