ANSI Common Lisp 25 Environment 25.1 The External Environment 25.1.4 Time
220.127.116.11 Universal Time
Universal time is an absolute time represented as a
single non-negative integer - the number of seconds since
midnight, January 1, 1900 GMT (ignoring leap seconds).
Thus the time 1 is 00:00:01 (that is, 12:00:01 a.m.) on January 1, 1900 GMT.
Similarly, the time 2398291201 corresponds to time 00:00:01 on January 1,
Recall that the year 1900 was not a leap year; for the purposes of
Common Lisp, a year is a leap year if and only if its number is divisible by 4,
except that years divisible by 100 are not leap years, except that years
divisible by 400 are leap years. Therefore the year 2000 will
be a leap year.
Because universal time must be a non-negative integer,
times before the base time of midnight, January 1, 1900 GMT cannot be processed by Common Lisp.
Defined names involving time in Universal Time.