Number of seconds since Epoch

 

If'@', Indicates the internal timestamp of a second. A number can contain an internal decimal point ('.'Or','); Any number beyond the supported range will be truncated. This number cannot be combined with other date items. It provides a complete timestamp.

 

In a computer, the time is expressed in seconds since the epoch-a clearly defined time point. On GNU and posixposix systems, the epoch is 00:00:00 UTC ,'@ 0'That is, this time ,'@ 1'Indicates that the time is 00:00:01 UTC, and so on. GNU and Most POSIX-compatible systems support POSIX extensions and can use negative numbers'@-1'-1' indicates 23:59:59 UTC.

 

The traditional UNIX system uses a 32-bit integer to calculate the number of seconds, which can represent the time range from 20:45:52 to 03:14:07 UTC. The new system uses 64-bit computing to calculate the second and the second, which can represent the known cosmic time accurate to 1 second.

 

In most systems, the second Skip is ignored during computing. For example, most systems'915148799'Indicates 23:59:59 UTC ,'915148800'Indicates 00:00:00 UTC, but there is no representation between 23: 59: 60 UTC.

 

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As shown in the gettimeofday function, gettimeofday is the number of seconds since the Unix epoch. If you use the long type to store seconds, on a 32-bit machine, it can represent the number of seconds in almost 70 years.