Got recommended for UCMJ by My E7 for being late, meanwhile I have 29 days left before I start clearing for ETS what are the the outcomes?

The outcome is up to your commander. You can't be retained past your ETS for NJP only a court martial but you can still be punished if the commander sees fit

Why did he recommend UCMJ if you haven't ever been late before or had any other issues? That seems odd - but the most he can do is recommend. If the commander doesn't see any justification in it, it won't go anywhere.

What's his supporting documentation to recommend you for whatever he recommended you for? It's not gonna pass legal if there's no supporting documentation like counselings at a minimum.

If it does, like said you get flagged until it's done.

Assuming the chain of command concurs and proceeds with UCMJ action, you get flagged and go through the UCMJ process. If it's a Courts Martial, you can be held past your ETS, but not otherwise.

Here's a similair question with relevant documentation...

http://asktop.net/q-and-a/can-i-be-held-past-my-ets-date-for-an-administrative-separation-board/?all=1