My kid is born on February 28 in 2003. Otherwise, he may have been born one day later on a leap year and become a leap year baby.

So, why do we have an extra day in the month of February? Why only once every four year? Why didn’t they make February 30 days or 31 days like other months? Is there an explanation to it?

Now, I am going to put the explanation from Wiki to explain it to my children :

A leap year (or intercalary year) is a year containing one or more extra days (or, in case of lunisolar calendars, an extra month) in order to keep the calendar year synchronised with the astronomical or seasonal year. For example, February would have 29 days in a leap year instead of the usual 28. Seasons and astronomical events do not repeat at an exact number of full days, so a calendar which had the same number of days in each year would over time drift with respect to the event it was supposed to track. By occasionally inserting (or intercalating) an additional day or month into the year, the drift can be corrected. A year which is not a leap year is called a common year.