What day/date; Which day/date

1. What day do you have your music lesson? (by a Taiwanese teacher of English)
2. What date do you have your music lesson? (by a Taiwanese teacher of English)
3. Which day do you have your music lesson? (by Michael Swan, 451.5 of Practical English Usage)
4. Which date do you have your music lesson? (by a Taiwanese teacher of English)

What's the difference in meaning between the above sentences?