In the first release of Unix (November 1971), the page for the system time of the time stated that it returned “time from 00:00”: 00, January 1, 1971, measured in sixties. ”This was a 32-bit value, so it was even considered as unsigned, it could only track about 2.26 years after that date, however the man page and comments on the source code describe the system call as "get the time of year", the year cannot be, and and (used to format the date and time) did not format the year or even worked correctly with time values greater than 1 year, so it is likely that the date will be manually reset every year and 1971 on the manual page is insignificant. Well, with the exception of a small problem, that 1972 has an extra day; in this regard, a note was added to the error section : "The procedure must be reassembled for a leap year." Nice. date ctime()
In 1972, the manual page for the system time was changed to state that it returned time from “00:00:00, Jan 1, 1972”, with a note: “The time is stored in 32 bits, which guarantees a crisis every 2.26 years "
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