---
created_at: '2014-04-15T12:45:57.000Z'
title: Did you ever wonder why December has 31 days? (1997)
url: http://projects.csail.mit.edu/gsb/old-archive/gsb-archive/gsb1997-02-14.html
author: soegaard
points: 113
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num_comments: 68
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created_at_i: 1397565957
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objectID: '7591474'

---
[Source](http://projects.csail.mit.edu/gsb/old-archive/gsb-archive/gsb1997-02-14.html "Permalink to Calendar Reform")

# Calendar Reform

From: Oded Maron   
To: all-ai@ai.mit.edu  
Subject: GSB --- Friday at 5:30  
Date: Fri, 14 Feb 1997 21:21:40 GMT  

Did you ever wonder why December has 31 days? Well, I opened my 1911 Edition of the Encyclopedia Britanica (the preferred edition of Western scholars) and here is what it had to say: 

Julius Caesar (yes, the guy from the movie) decided to fix up the calendar, and give every other month 30 days, while the rest get 31 days. Of course, that gives you 366 days in a year, so February was picked to get hosed and it got only 29 days, but 30 on leap years. The calendar looked like this: 
    
    
     1   2   3   4   5   6   7   8   9  10  11  12  month
    31  29  31  30  31  30  31  30  31  30  31  30  number of days
    

Pretty simple, right? Well, Julius thought so too and for the good job he has done, he rewarded himself with an $80 million check. No, wait, that's Orvitz. Julius rewarded himself by naming month #7 after himself: July. 

A couple of Roman leaders later, Augustus decided that he too deserved to have a month named after him (kind of like presidential libraries), so he changed the name of month #8 to be August. But now August has only 30 days compared to July's 31. Does that mean that Augustus is only 97% the leader that Julius was? 

Yes. So Augustus made August have 31 days. Now you had 3 months in a row with 31 days and that is unseemly. So September lost one, October gained one, November lost one and December gained one. Now the calendar looked like this: 
    
    
     1   2   3   4   5   6   7   8   9  10  11  12  month
    31  29  31  30  31  30  31  31  30  31  30  31  number of days
    

But now you had 366 days in a non-leap year, so February got the short end of the stick _again_ and lost a day. So our calendar is messed up because of that "big stinking dufus, Augustus". 

Come and for a fun and educational time at this week's 
    
    
      G   I   R   L     S   C   O   U   T     B   E   N   E   F   I   T

5:30 pm February 14, 1997 7th floor playroom 

