When Pope Gregory altered the calendar in 1582 to get it in synch with the seasons, protesters marched in the streets demanding the return of their 11 days.
And anybody with a birthday on 31 May could now face losing it, if an astrophysicist and an economist have their way.
Richard Conn Henry and Steve Hanke of the Johns Hopkins University have used computer programs and mathematical formulas to create a new calendar in which each new 12-month period is identical from one year to the next.
"Our plan offers a stable calendar that is absolutely identical from year to year and which allows the permanent, rational planning of annual activities, from school to work holidays," says Henry.
"Think about how much time and effort are expended each year in redesigning the calendar of every single organization in the world and it becomes obvious that our calendar would make life much simpler and would have noteworthy benefits."
Under the Hanke-Henry Permanent Calendar, if Christmas fell on a Sunday in 2012 -and it would - it would take place on a Sunday for ever after.
Achieving this means, first, altering the numbers of days in the months - so that March, June, September and December would all have 31 days, with the rest all having 30.
Because the year is, inconveniently, 365.2422 days long, an extra adjustment is needed. Hanke and Henry propose dropping leap years entirely in favor of an extra week added at the end of December every five or six years. This brings the calendar in sync with the seasonal changes as the Earth circles the sun.
Economist Hanke says making the change would make bankers' lives simpler - something we all want, obviously.
"Our calendar would simplify financial calculations and eliminate what we call the 'rip off' factor'. Determining how much interest accrues on mortgages, bonds, forward rate agreements, swaps and others, day counts are required," he says.
"Our current calendar is full of anomalies that have led to the establishment of a wide range of conventions that attempt to simplify interest calculations. Our proposed permanent calendar has a predictable 91-day quarterly pattern of two months of 30 days and a third month of 31 days, which does away with the need for artificial day count conventions."
But Hanke and Henry don't just want to change the calendar - they want to change time, too. We should scrap world time zones and all stick to Universal Time, they say.
"One time throughout the world, one date throughout the world," they proclaim.
"Business meetings, sports schedules and school calendars would be identical every year. Today's cacophony of time zones, daylight savings times and calendar fluctuations, year after year, would be over."