The trouble with designing a nice, regular calendar is that each Earth year is 365.2422 days long, leaving extra snippets of time that don't fit nicely into a cycle of 24-hour days. If this time isn't somehow accounted for, the calendar "drifts" relative to the seasons, and the next thing you know, Christmas Day is coming after the spring thaw.
"The Gregorian calendar deals with this by adding an extra day (Leap Day) to February about every four years, correcting for the seasonal drift.
"It's really incredible that in the Middle Ages, they were able to invent a new calendar that was so accurate," Henry told LiveScience. What bothers him about the Gregorian calendar, though, is the frustrating tendency for days of the week to jump around. Because 365 is not a multiple of seven, 7-day weeks don't fit evenly into the Gregorian calendar. That means that each year, dates shift over one day of the week (two during leap years).
Under the Hanke-Henry Permanent Calendar (named after Henry and Steve Hanke, a Johns Hopkins economist who also advocates calendar overhaul), every date falls on the same day of the week — forever.
"Everybody has to redo their calendars," Henry said....
The calendar follows a pattern of two 30-day months followed by one 31-day month. That means the old rhyme, "30 days hath September, April, June and November," would need to be revised to "31 days hath September, June, March and December."
To account for extra time, Hanke and Henry drop leap years and instead create a "leap week" at the end of December every five or six years. This extra week, dubbed "Xtr," would adjust for seasonal drift while keeping the 7-day cycle on track."
http://www.msnbc.msn.com/id/45828666/ns/technology_and_science-science/#.Tv8ap5iEPNk
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