1. 6-8 hours of sleep is required for every human being.
2. Ideally, one should sleep 3-4 hours after taking dinner and wake up before sunrise.
3.For those who working in night shifts, they can compensate by sleeping half of their original sleeping time (3-4 hours) in the day time.
4. Sleeping after lunch or in the evenings is strictly prohibited as it causes aggrevation of all 3 doshas (vata,pitta and kapha) and this is one of the major causes of many diseases including diabetes, thyroid dysfunction etc.