The bug

When using /time set, the time does not actually get set to the value you tell it to. Instead, the command gets transformed into a /time add command with a value between 0 and 24000, making various things impossible.

How to reproduce

1. Create a new world
2. /time set 0
→ It set the time to 24000 instead of 0
3. /time set 100000
→ It set the time to 28000 instead of 100000

Consequences

This makes /time set just /time add, but worse. Two things that very obviously should be possible with /time set are not:

• Going back to a previous day (even though /time add can do it just fine)
• Skipping ahead more than one day (even though /time add can do it just fine)

For example, a very common use of /time set is going to a specific moon phase. /time set 14000 should give you a full moon. Instead, it gives you the "next" moon phase, which is not at all what you specified. If you wanted to go to the next moon, you would have used /time add.