Nintendo are gearing up for the big event, but despite what has been revealed already, they had yet to provide a length of time the presentation will go on for.
Thankfully in a Nintendo Everything pointed out article, Niconico has the answer as their timetable shows the presentation as lasting only an hour. Now this does make perfect sense, because while it is the Big Switch presentation, it is also being classed as Nintendo Switch Direct. While some Nintendo Directs can be quite long, most are well under an hour and an hour is plenty of time to show off at least 10 games and talk specs and still have plenty to talk about and reveal in the coming weeks.
Additionally, although Tatsumi Kimishima, the President of Nintendo is known to be presenting the event, it is not quite yet known if he will be presenting the entire thing, or just some of it, with other presenters taking over when their turn comes around.
Lastly, should you wish to watch the presentation, which could stop a few minutes less of a full hour or even go a little over, these are the times the one hour presentation is set to occur:
20:00 p.m. PT (January 12th)
23:00 p.m. ET (January 12th)
04:00 a.m. in the UK (January 13th)
05:00 a.m. in Europe (January 13th)
Source: Niconico via Nintendo Everything