Nick Toncoop, age 11, of St. Catharine's Ont., for his question:

How long is a solar year?

The solar year is the period of time it takes the earth to travel from one Vernal Equinox to the: next. This is the time it takes to complete one journey around the sun ‑ 365 days, five hours, 45 minutes and 46.575 seconds. The solar your also is called the tropical year, the astronomical year, the equinoctial year and the natural year. It is shorter than the sidereal year, which is the time it takes the earth's center to cross and recross a given star.

Our calendar is based on the solar year, which is about 365 days long. We gather up these four extra quarter days from four solar years every leap year. Then, every fourth year, we take care of this surplus by adding an extra day to the calendar.