What does x on the ID really mean?

Life, whether you are taking the train, or to handle a variety of formalities, need to use the identity card, it has become a very important part of our lives, but about the identity card itself, you know how much?

Someone will say, why my ID card written on the effective time is 10, and some people's time is 20? Now let's have a look!

First, the validity period

The validity period of the identity card is divided into 10 years, 20, three kinds of long term. 16 to 25 years of age, issued a valid for 10 years of identity card, 26 to 45 years of age, issued a valid for 20 year of identity card; The age of 46 or above, issued to a long-term valid identity card. The validity period of the document is calculated from the date of issue. If a person is born September 20, 1990, 18 years of age in 2008 to apply for identity card, the issue date is December 31, 2008, he belongs to the age of 16-25 years, the validity period of the document belongs to 10 this grade, until December 30, 2018 full.

Then, some people will ask, why the Beijing identity card is 1, and Henan is the beginning of 4? What does the figure on the ID card mean?

Second, the number composition

1. Address Code

(the first six digits of the ID number) represents the code of the county (city, Town, district) of the resident account. 1-2 provinces, autonomous regions, municipalities code; 3-4 prefecture-level cities, provinces, Autonomous Prefecture code, 5-6 counties, county-level, district code.

2. Birth date Code

(ID number seventh to 14th) indicates the year, month, and day of the encoded object's birth, where the year is represented by a four-digit number, with no separator between the year, month, and day. For example: May 11, 1981 is 19810511.

3. Sequential code

(ID number 15th to 17 digits) address code identifies the area within the range, the same year, month, day of birth of the person to set the order number. The 17th digit was given to men in odd numbers, even to females.

4. Check code

(The last digit of the identity card number) is a test code calculated according to the previous 17-digit code, according to the ISO 7064:1983.mod 11-2 check code. As the tail number check code, is calculated by the number coding unit according to the uniform formula.

So why would someone's ID be behind the number x?

If someone's tail number is 0-9, will not appear x, but if tail number is 10, then you have to use X instead, because if 10 do tail number, then the person's identity card becomes 19 bits, and 19 digits of the number violates the national standard, and China's computer application system does not recognize the 19-digit ID card number. Ⅹ is the Roman numeral 10, uses the X to replace 10, may guarantee the citizen's identity card to conform to the national standard.

What does x on the ID really mean?