1. In 46 BC, Julius Caesar, commander-in-chief of Rome, specified the calendar. Because he was born in July, in order to show his greatness, he decided to change July to "Julian month", and all single months were stipulated as 3 1 day, and bimonthly was 30 days. In this way, there is one more day in a year. February was the month when prisoners were executed in ancient Rome. In order to reduce the number of people executed, 1 day was reduced in February to 29 days.

Augustus, Caesar's heir, was born in August. Following Caesar's practice, he added 1 day as "August", changed 10 and1February to 3 1 day, and changed September 1 1 month to 30 days. There are 1 day in the whole year, and he has reduced 1 day since February, so February has become 28 days, and there are only 29 days in leap years.

In this way, there will be a big month in a single month before July, and a big month in two months after July, February 28.

More than 300 years ago, a British mathematician first used the multiplication symbol "×". Because multiplication is a special addition, he marked the plus sign obliquely.

It is said that as early as 4,000 to 5,000 years ago, our ancestors used a drip instrument to measure time. This instrument is called lettering.

"Tangram" is a kind of ancient tangram in China, which is made up of seven pieces into a big square with various patterns. Later, it spread abroad and was called "Tangtu". "Tangram" has spread to today and become a kind of intellectual toy that people like.

The symbols "+"and "-"were first used by a German 500 years ago. At that time, they didn't mean "plus" or "minus". It was not until more than 300 years ago that it was officially used to mean "addition" and "subtraction".