The technical yesterday when you haven't gone to sleep yet. When it's two am, you'd count the evening as part of today since you haven't gone to sleep yet. But you can't do this because it's technically a new day. So yesterday becomes yestertoday until you go to sleep or pass out.
4am at a kebab shop: "I just heard about this place from a friend yestertoday!"
by Solarion January 25, 2010