The answer to this question may seem obvious, right? 365 days. Everyone knows that. However, nature is often not so simple. Think about it; what are the odds that the day (which is made up of 24 hours and each hour is 60 seconds) just happened to align so perfectly with the rotation of the Earth? The answer is very low. Such a low probability that it is almost impossible. In fact, this would be the same as having circumference of the Earth being exactly 1000 kilometers or the sun being exactly 100 degrees Celsius. Such coincidences don’t happen on accident. This was the line of thinking that led me to learn about both the history and length of a year: about 365.2425 days.

I first started with the history of the calendar. How did people find out how long it took for the Earth to rotate around the Sun? It started out quite simply. People knew that the seasons happened in a cycle, and if they could predict when the next harvest season would be, they could grow even more food. So, people started to track the days until the next cycle. This was better than nothing, but the seasons often changed lengths, and this resulted in varying and inaccurate results. As civilizations progressed, people began using different methods. The lunar calendar, Egyptian calendar, and Julian calendar were eventually developed. The Julian calendar predicted the length of a year to be 365.25 days! Surprisingly accurate!

This calendar remained in use for hundreds of years but eventually became inaccurate. In fact, it ended up being *10 days *behind at the time of it’s disposal. I guess you can say: it retired early. The Julian calendar may have been gone, but it’s legacy lived on through the Gregorian Calendar. This is the same calendar we use today and has some minor adjustments from it’s predecessor; every leap year is the same unless it is divisible by 100. However, if the year is divisible by 400, then it is counted. This system gives us an estimation of 365.2425 days in a year.

Even the system we use today is not 100% perfect, it has an error rate of approximately 0.03% . To further add to this problem, orbital variations changes the length of a year by .00005 days per 1,000 years. What does this all mean? It means that we can never know the exact length of a year, we can only approximate very accurately.

Often, the simplest things we take for granted are the most complicated. This is what I have learned in my *years* of life. Wait a second, how long have I been alive?

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