The two-hour maintenance window will run from 7-9 p.m. ET tonight, Jan. 6. Online play, rankings and more in Pokémon X and Y may be unavailable during that time.
This period is separate from Nintendo's regularly scheduled maintenance windows, which run on Mondays from 3-7 p.m. ET for Wii U and Nintendo 3DS, and on Tuesdays from 2-6 a.m. ET for Wii and Nintendo DS.