Nintendo UK sent out an announcement about the Nintendo Switch Presentation. It will begin at 8 PM PT / 11 PM ET on January 12, which is 4 AM in the UK / 5 AM in Europe on January 13.
In the announcement, Nintendo says that the live stream will be broadcast in Japanese, but there will be English voiceover during the presentation. Hopefully that works out okay and is not confusing. As well, Nintendo stated that key announcements will be shared on the Nintendo UK Twitter, while Nintendo of America has not said anything yet but will no doubt do so soon.
There is a livestream set up on Nintendo’s Japanese YouTube account, and there will no doubt be one for the various European accounts and Nintendo of America as well. This will also be viewable from the official site as well as twitch at the same time.
Source: Nintendo PR