Time converter here. Find your city and watch what day it is since for those of us in the USA it's actually going to be on Tuesday night that the work wil occur.
Even though the window is going to be 2 hours in length, LiveJournal will not be down that entire time. Just be aware that *during* this 2 hour window, connectivity may be slow or timeout completely.
Details are in this lj_maintenance entry, see point #1 which we had to postpone until we got the extra parts in.