The Pokémon Global Link website announced the details for the 3rd Pokémon Sun and Moon Global Mission. "Trade Pokémon at the GTS!" will take place from January 30th, 2017 until February 14th, 2017 at 00:00 UTC.

Participate in the New “Trade Pokémon at the GTS!” Global Mission

The “Trade Pokémon at the GTS!” global mission is active in Pokémon Sun and Pokémon Moon through February 14, 2017, at 00:00 UTC. Remember to use Game Sync to contribute your tally of trades via the Global Trade Station to the total!

If everyone teams up to make 1 million trades at the GTS, you’ll receive 2,000 Festival Coins.

If you've signed up for a PGL account before the global mission ends and the global goal reaches 1 million trades at the GTS, you’ll receive 4,000 Festival Coins—but if 2 million trades are registered then the reward will also include a Friend Ball!

If the goal isn’t reached, you’ll still receive 200 Festival Coins for participating, while PGL members receive 400 FC.

Here’s how you can join the fun:
1. Talk with the global mission receptionist in the Festival Plaza castle and enter the global mission.
2. Back at the Festival Plaza, select Trade and then GTS.
3. Trade as many Pokémon as possible at the GTS before February 14, 2017, at 00:00 UTC.
​4. Check in with the global mission receptionist in Festival Plaza before February 14, 2017, at 00:00 UTC to record your progress.

You don’t need to be a Pokémon Global Link member to participate in global missions, but as a bonus, players who have registered their Game Sync ID at the PGL will earn double the Festival Coins, and any PGL member who reports five or more trades will earn five Rare Candies!

Source: https://3ds.pokemon-gl.com/information/58dccacf-34eb-4d1e-accc-4313cf82d5b5