The day after New Years. You had a little to much to drink that last day of the year and now for the first dayof the new year you can celebrate with all the other hungover people, or you could sleep.
Person 1: Dude my head kills from last night.

Person 2: Another typical hangover Day.
by Sarah Is Beast December 31, 2008
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AKA New Years Day (not to be confused with New Year's Eve)

It is called Hangover Day because..
well it's obvious

everyone has a hangover today because of excessive drinking at New Year's Eve parties.
Sober Person: Hey Lofonduh, wanna go to the mall today?

Lofonduh: Naww.. my head hurts too much.

Sober Person: But no one will come!

Lofonduh: That's because it's Hangover Day.
by Rickey Minouwagaincity December 22, 2008
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I woke up next to five bottles of Jägermeister and a pile of confetti on National Hangover Day.
by Limbo December 26, 2005
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1st January 12PM or before and lasts to 2nd (this is national hangover day), 3rd, or if its really bad, 4th January (these are local hangover days). Perfect day to do crimes, because nobody cares. But the entire country will think the robber is a loser because he doesnt have hangover.
Person 1: Hey, wanna do something funny 1st January?
Person 2: Dude, its National Hangover Day
Person 1: Oh yeah, right ..
by Jellies January 10, 2007
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The day following any popular holiday.

Including but not limited to the day after:
New Years Eve (New Years Day)
The Super Bowl
Memorial Day
Fourth of July
Labor Day
Thanksgiving (Black Friday)
Christmas (Boxing Day)
Girl: I'm not getting any work done today, I'm just wasting time.
Boy: It's okay, it's National Hangover Day, a lot of people are wasting time.
by Fun Johnny February 7, 2011
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December 26th, the day after Christmas. The day where nobody has the energy or will power to get there hung over asses out of bed after a hard night of drinking, present opening, face stuffing, fucking (if your lucky), disapointment, and in some cases humiliation and shame. A day that is usually celebrated by staying in bed till 4 and finally getting up only to spend the rest of the day vomiting your guts out.
Guy1: Christmas is gonna be awsome this year!!!! Guy2: Hell yeah!!!! But fuck man, I sure ain't looking forward to National Hangover Day... Guy1: Fuck it, we'll just be in bed all day anyways, so no need to worry about it.
by Xero _ Manifest December 25, 2010
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