Analysis: 12 has three birthdays, 12÷3=4, which means that Xiao Qiang has a birthday every four years. Generally speaking, every four years is a leap year, which means that Xiao Qiang was born in a leap year and February has 29 days, so Xiao Qiang was born on February 29th of a leap year.

The establishment of leap year is to make up for the time difference between the number of days in a year and the actual period of revolution of the earth caused by man-made calendar regulations. The year to make up for the time difference is leap year. The leap year in the solar calendar has 366 days and February 29 days; The normal year of the solar calendar is 365 days, February 28th.

Extended data 1. Judgment method

1. To judge whether a year is a leap year, you only need to look at the last two digits of the year. If the last two digits are divisible by 4, it is a leap year, otherwise it is not.

2. When the last two digits are all 0, we will look at the first two digits of the year; If the first two digits are divisible by 4, it is a leap year, and vice versa.

3. If the two digits at the end of 2004 are 04, it can be directly regarded as 1 digit. If this number is divisible by 4, it is a leap year, otherwise it is not.

Second, the calculation method

1, 4 years 1 leap, 97 leap, 3,200 leap and 86,400 leap in 400 years (27 * (97*8- 1)+ 1).

2, 4 years 1 leap, 128 3 1 leap, 86400 (675 * 3 1+0) leap (20926 leap).

Baidu encyclopedia-leap year

Baidu encyclopedia-leap year