Observance of Yom Kippur has many aspects. It is a day of fasting (not eating any food or drinking anything including water). It is usually a day of prayer and study. As Yom Kippur is an extremely important day, there are many traditions around it. Some Jews will not wear leather on Yom Kippur. Some wear mourning clothes or even the ritual clothes that they plan to be buried in. Yom Kippur falls on the 10th day of Tishri and is also the last of the "Days of Awe". It never occurs on a Sunday, Tuesday or Friday.