The Lost Eleven Days

Have you ever gone to bed one night and wondered just where the day went? Well could you imagine waking up to discover that eleven days had vanished completely? That is just what happened in 1752 when the entire inhabitants of Britain and America went to bed on Wednesday 2 September, only to awake on Thursday 14 September.

However, it wasn't an epidemic of sleepy sickness or even a mass dose of laziness that kept the entire populace in bed but merely the authorities attempting to synchronise with the rest of the world by adopting the Gregorian calendar.

The Julian calendar (named after Julius Caesar) had been in use since biblical times but was finally phased out throughout Europe in the 1582 but it took the resolute Brits and Americans another two hundred years to follow suit.

And if the painter Hogarth is to be believed the populace didn't take too kindly to it either, with people taking to the street demanding the return of their missing 11 days and even reports of rioting.

Then why change? That was what the British authorities had been saying for two hundred years ever since Pope Gregory XIII had replaced the Julian calendar in Europe two hundred years before.

However, the reason for the original change was that the Julian calendar didn't allow for enough leap years (they were omitted in years divisible by 100 but not divisible by 400 - what were the Romans thinking?) and the seasons were slowly becoming out of sync with the calendar. The situation was now becoming even more intolerable in Britain, playing havoc for farmers - who had no idea when to plant their crops, finally the authorities were to switch over and fast forward the whole country 11 days.

However this synchronisation problem has always been with us. We have traditionally tried to base our calendars around the movement of the Earth to allow us to predict seasons and know when the summer and winter will fall. However, we may have sorted out the leap years (caused by the fact the Earth takes 365 and a quarter days to travel around the Sun) but trying to base a calendar around the movement of the Earth will always lead to problems.

The Gregorian calendar worked fine until the 1950's when the atomic clock was developed. The atomic clock worked so well - providing timing information accurate to a second in several millions of years - that we soon realised that our clocks were now far more accurate than the Earth itself.

The Earth is actually slowing down in rotation and if nothing was done then eventually noon would fall at night and vice-versa (albeit not for several millennia) but don't worry you are not about to wake up in the middle of next week. The solution is the adding of leap seconds and 33 have been slotted into the end of our years since the 1970's.

The decision to insert a second is usually taken six months before after careful monitoring of the Earth's rotation. A calendar based on the movement of the Earth may seem less relevant today but with a Global Positioning System (GPS), a global time-scale (Coordinated Universal Time), and computers all synced together around the world using NTP servers (Network Time Protocol) it is imperative we can all tell the right time.


Richard N Williams is a technical author and a specialist in the telecommunications and network time synchronisation industry helping to develop dedicated time server products; ethernet clocks, GPS time servers, NTP servers, digital wall clocks, atomic clock servers and SNTP time servers. Please visit us for more information about a GPS time server or other NTP server products.