Frazz by Jef Mallett for January 30, 2009
Transcript:
Caulfield says, "Check it out: January has 31 days." Caulfield says, "February has 28. March jumps back to 31." Caulfield says, "31 plus 28 plus 31 divided by 3 equals 30. So why not just make all three months 30 days?" Frazz says, "What brought on all these calculations?" Caulfield says, "Avoiding my math homework, mostly."
March used to be the start of the year (note that September means the seventh month when it is now the ninth) so February was just the days left over (usually – https://en.wikipedia.org/wiki/February )