Time is a strange thing. On one hand there are clearly observable phenomenon that determine our perception of time passing: The sun rising and setting signalling the passing of a day, the phases of the moon, the seasons, but these partitions are not objective in any sense, since they only hold true on earth. There is nothing inherently sensible about parting a day into 24 hours, or even how long an hour should be. It's all conventions we have come up with because it makes sense to us here on earth. But if it's a convention, how did we come up with it? and has it always been that way or have there been other attempts to create a system for recording the passing of time?
The system used today in most of the world is called the Gregorian Calendar and it was introduced in October 1582 by Pope Gregory XIII, making our current way of recording the passing of time perhaps younger than many would assume, but perhaps less surprising when one considers that before the Gregorian Calendar there were several other attempts.
The direct predecessors to this calendar were invented in the Roman Empire. The Romans themselves believed that their first calendar was invented by Romulus, one of the founders of Rome. This calendar consisted of 10 months, starting in what we call March:
Martius - 31 Days Aprilis - 30 Days Maius - 31 Days Iunius - 30 Days Quintilis - 31 Days Sextilis - 30 Days September - 30 Days October - 31 Days November - 30 Days December - 30 Days
Reading the names, it will become obvious to anyone who knows a bit of latin that from the fifth month onwards, the months' names all correspond to their order in the row. Deci in latin means ten, making December the logical tenth month. In our modern system that is not the case and may be confusing for some people whose languages still have a strong similarity to latin where counting is concerned.
The system however was badly flawed in that it only accounted for 304 days a year, leaving about 61 days unaccounted for. Some time around 700 BC this was improved upon by by King Numa Pompilius, who reduced the number of days in the 30-day months to 29 days, and added two months of respectively 29 days: January (Ianuarius), and 28 days: February (Februarius). This brought the calendar up to 355 days, which is still about ten days short, but much better than the previous 61 missing days.
To make up for the missing days, some years had an additional 'month' added to them to realign the months with the seasons and lunar cycles. Theoretically the extra month should be inserted into the calendar every other year, but it does not seem it was strictly followed, though it is hard to tell exactly, as this happened a very long time ago. What is known is that it was inserted between February and March when it did occur and that it seemed February was often shortened a little in the process.
In year 45 BC Julius Caesar introduced the Julian calendar. It changed the lengths of the months and got rid of the additional month and instead instituted leap years, much the same way we know today. In fact the lengths of months in the Julian and Gregorian calendars are exactly the same, but the frequency of leap years aren't. In the Julian Calendar a year is usually 365 days long and every fourth year there is a leap year where a single day is added to February, making the month 29 days long and therefore making that year 366 days instead of the regular 365. That makes the average year 365,25 days long. If you are thinking, that sounds exactly like the way we handle it now, you are not wrong. That is the way we do almost all the time, with the small, but significant difference that in the Gregorian Calendar a further two conditions are added: if the year is exactly divisible by 100 it will not be a leap year, unless it is exactly divisible by 400. That makes the average year 365,2425 days long, which is extremely close to the astronomical reality.
Scientifics are slightly geeky additions that have been with us since the eagle has known how to fly. Okay, not that long, but it's a nifty category that separates it from the usual ramble of articles.