2. 1 year = 12 months;

3. 1 month =30 days;

4. 1 day =24 hours;

5. 1 hour =60 minutes;

6. 1 min =60 seconds;

7. 1 sec = 1000 ms;

8. 1 ms = 1000 microseconds;

9. 1 microsecond = 1000 nanosecond;

10, 1 nanosecond = 1000 picosecond.

Origin:

1, year month day

According to the alternation of day and night caused by the rotation of the earth, people formed the concept of "day"; According to the concept that the moon revolves around the earth to form a "moon" and the concept that the seasons alternate to form a "year" caused by the earth's revolution around the sun.

2. Time

It is an auxiliary time unit, which is in harmony with the basic unit of the international system of units. Except leap second, one hour is generally equal to 3600 seconds, or 60 minutes, or 1/24 days. "H" is often used in English or mathematics.

3. Point

Minute is English, which means "tiny" and also means min. Engraving = 15 minutes, word =5 minutes (usage in southern Fujian and Guangdong).

4 seconds

Seconds is the basic unit of time in the international system of units, with the symbol S, sometimes marked with English abbreviations as sec.