What it does?
A Day/Night detector is a daylight sensor connected to an Input.
This is 2 Designs showing a very small Night detector and to give you an example a Day sensor as well.

Uses -
1. Make it so a button only works at Night or Day.
2. Make something happen at a specific time of day (adding redstone to extend a signal before touching the redstone torch or the output.)
3. Farming where it does the harvesting at a specific time of day.

No download since there is no hidden redstone.

If you like it, give it a diamond or a comment.
want to see what I'm up to ? twitter.com/RedstoneMagic
If you don't like it, your opinion, give me a reason why you dislike it in the comment section.
Have fun, create creations, compact if you wish and see you later!

-RedstoneMagician