The concept GMT UTC time zone

Timestamp

Definition: GMT January 1, 1970 00 hours 00 minutes 00 seconds ( Beijing time on January 1, 1970 08 hours 00 minutes 00 seconds ) until now the total number of seconds, expressed as: 1970-01-01 00:00:00 UTC.

It called Unix time (Unix time), POSIX time (POSIX time).

We can see from the definition, global same time, no matter what your time zone, a time stamp is the same , the time stamp is changed will not follow the zone change. With a time stamp to indicate the time the world are the same

The same time stamp, in different time zones, times are different: a time stamp, such as 1520411719, corresponding to a GMT: 2018-03-07 16:35:19 GMT + 8, this case corresponding to the time Washington: 2018-03- 07 03:35:19 GMT-5, which is why we often say that time.

 

Greenwich Mean Time (GMT)

When it refers to the outskirts of London, UK Royal Greenwich Observatory, the local mean solar time, because the prime meridian is defined as the warp there.

 

Coordinated Universal Time (UTC)

Coordinated Universal Time (English: Coordinated Universal Time abbreviated UTC) is the most important in the world time standard, which is based on atomic seconds long, as close as possible GMT on time .

Coordinated Universal Time is adjusted world clock and time the main standard time, it does not differ by more than 1 second [4] and 0 degrees longitude flat sun, do not comply with daylight saving time.

Coordinated Universal Time is the one closest to Greenwich Mean Time (GMT) time of several alternative systems.

For most purposes, UTC time is considered interchangeable with the GMT time .

For example, now there is a log that time stamp is 1570987357 (the timestamp is from my https://tool.lu/timestamp/  acquired),

Then the time stamp corresponding GMT: [2019-10-13 17:22:00 may be implemented by SQL]

select from_unixtime(1570987357,'yyyy-MM-dd HH:mm:SS');
-- 2019-10-13 17:22:00

But my local time (GMT) for the 2019-10-13 01:22:00,

This function also verifies the hive from_unixtime GMT time is obtained, then the obtained time stamp corresponding to local time by way of distinguishing GMT +