Time to sleep and learn as per vedas

 Assuming standard sunrise & sunset at 6am & 6pm, the day is divided into different parts for different activities:

4.24am - 6 - brahma muhurtham (actually 2 muhurtams, since 1 muhurtam = 48 minutes) - snanam, sandhyavandanam

6 - 8.24 - pratah kalah - veda adhyanana (learning)

8.24 - 10.48 - sangava kala - danam (both giving & taking), items for puja

10.48 - 1.12 - madhyanika kala - madhyanika sandhya, tarpana, vaisvadeva, ijjai (bhagavad aradhana/neivedyam), manushya yagna (feeding athithis), finally bhojana (if no sraddham on that day)

1.12 - 3.36 - aparahna kala - sradhham, purana adhyanana, veda adhyapana (teaching)

3.36 - 6 - sayam kala - snanam, sandhyavandanam

6 - 7.24 - bhojana

7.24 - 9.48 - bhoga

9.48pm - 4.24am - nidra (sleep) - (Ideal 10pm to 5am/6am)

Chapter 49, Sṛṣṭi-khaṇḍa, Padma-Purāṇa

देवानामेकभुक्तं तु द्विभुक्तं स्यान्नरस्य च ॥ १२७.ख ॥

त्रिभुक्तं प्रेतदैत्यस्य चतुर्थं कौणपस्य तु ॥ १२८.क ॥

Gods eat once only, men eat twice, spirits and demons eat thrice and those who feed on dead bodies eat four times (a day).