I would write a letter like this when requesting a day's leave from your boss:
Your City, State, Postal/Zip Code
Your Phone Number
City, State, Postal/Zip Code
Dear Mr./Ms. Last Name:
I would like to request a one day leave of absence on 7th November for personal reasons.
If approved, I will not be contactable on my home telephone number on this day, but I would be glad to assist with any questions via email or my mobile phone.
Thank you very much for your consideration.
Your Typed Name
Remember to keep a copy of the letter for your records so that you can verify it later, a copy will also remain on your employment file.
I hope that helps, good luck with your request, I hope it is granted.