Is there any command that can let a player sleep in the morning? If so, what is the command and how is it used?
61 Answer
As of version 1.8, there is no command (or other method) in vanilla Minecraft to allow players to sleep in the morning or during the day. But depending on what you're actually trying to accomplish, there may be other options.
If you want to fast-forward time, use the /time command. To add 8 hours to the clock use:
/time add 8000
To set the time to dawn (this will allow you to sleep in a bed) use:
/time set 13000
You could even make a command block programmed with time add 100 execute multiple times in order to create the illusion that time is passing by faster. Lots of ways to get creative, but unfortunately there aren't too many tools for you to use.