According to ayurveda, time periods in a day are dominated by the three doshas. Vata dominance is from 2AM-6AM and 2PM-6PM, Kapha is from 6AM-10AM and 6PM-10PM and Pitta is from 10AM-2PM and 10PM-2AM. Vata is known for movement, so during this period there is heightened mental alertness. Pitta time is good for physical activities and the body digests not just food but the mind is actively trying to digest thoughts. Kapha time is slow, relaxed and easy going which is the best time for sleep.
So the best time to hit the bed is with the Kapha phase (6PM-10PM) ensuring that you avoid the next Pitta phase which will make it difficult to relax and sleep. And the best time to wake up is before the next Kapha phase (6AM-10AM) as it causes ama (toxins) to accumulate in the srotas (channels) and creates a dull, tired feeling. This also ensures that you receive a restful 7-8 hours of sleep. Sleeping early will make it impossible for you to lie in bed later than 6AM.
Avoid daytime napping and sticking to fixed sleeping and waking up times. This rhythm will keep the body in sync with nature leading to better health.