Detailed Instructions: You are given a passage. You need to construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is the whole paragraph. Avoid creating questions that can be answered correctly without actually understanding the paragraph.
Q: Man has been tracking time for tens of thousands of years. Beyond the daily cycle of the sun, what is there to use to track time? The moon and the stars.

It takes the moon about 29 1/2 days to go around the Earth, about a month. The word "month" is derived from the same root as the word "moon."

The Earth revolves around the Sun over the course of a year, but if you don't know that, it appears that the entire universe of stars revolve around the Earth and Sun. It takes about 365 1/4 days for the stars to go back to where they started, and that makes a year.

So the moon revolves around the Earth about 12 times a year, and thus we have 12 months.

But actually it takes fewer than 360 days for the moon to go around the Earth 12 times. The months had to be lengthened so that 12 months match one year. (Other societies used lunar calendars, which kept the month based on the moon's cycle.) 30 days per month would still make the year too short, and 31 days per month would make the year too long. Thus we have some months 30 days and others 31 (and one other).

Even still, the length of the year doesn't exactly match the revolution of the Earth around the Sun, so we make adjustments. Every four years, we add a day to February.

And still it's not perfect, so every 400 years, we don't add that day to February.

As for why February starts with only 28 days is not known for sure. There have been different explanations, but it comes down to someone a long time ago making a pretty odd decision.
A:
How did the calendar start? Why 31, 30 and 28-29? Why 12 months?