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AbsoluteTime

Status: Stable

documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

Description

AbsoluteTime[]
    gives the total number of seconds since the beginning of January 1, 1900, in your time zone.
AbsoluteTime[date]
    gives the absolute time specification corresponding to the given date specification.

The supported date specifications are:
    {y, m, d, h, m, s}    DateList specification
    time            AbsoluteTime specification (a number, returned unchanged)

DateList entries may be elided from the right: {y}, {y, m}, {y, m, d}, etc. fill the
missing fields with {_, 1, 1, 0, 0, 0}. Day, hour, minute, and second values may be
noninteger; the year and month must be integers. Date lists are converted to standard
normalized form, so e.g. AbsoluteTime[{2022, 2, 31}] = AbsoluteTime[{2022, 3, 3}].

AbsoluteTime[] uses whatever date and time have been set on your computer system. It
performs no corrections for time zones, daylight saving time, or leap seconds.

Examples

No verified examples yet for this function.

Implementation notes

Algorithm. builtin_absolute_time returns seconds since the Mathematica epoch 1900-01-01. With no argument it reads time(NULL) + localtime, splits the broken-down time into y/m/d/h/m/s, and combines days_since_1900(...)*86400 + h*3600 + m*60 + s (returned as EXPR_REAL). A numeric argument passes through as an existing absolute-time spec. A {y,m,d,h,m,s} List (1–6 elements, defaults {y,1,1,0,0,0}) is converted the same way; year and month must be integral, while day/hour/minute/second may be fractional (the day's fractional part is folded into seconds). When all inputs are integral and the total is representable, it returns an exact EXPR_INTEGER, otherwise an EXPR_REAL.

Data structures. Day numbers come from days_since_1900, which applies the Fliegel–Van Flandern Julian-Day-Number formula (offset by the JDN of 1900-01-01) and normalises out-of-range months explicitly. ATTR_PROTECTED.

  • Protected.
  • Year and month must be integer-valued; day, hour, minute, and second may be noninteger.
  • Out-of-range date components are converted to standard normalized form, e.g. AbsoluteTime[{2022, 2, 31}] == AbsoluteTime[{2022, 3, 3}] == 3855254400.
  • Performs no corrections for time zones, daylight saving time, or leap seconds.
  • Returns an integer when every component is integer-valued and the total is exact; otherwise returns a real.

Attributes: Protected.

Implementation status

Stable — documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

References

Notes & additional examples

Worked examples

In[1]:= AbsoluteTime[]
Out[1]= 3.98985e+09

Notes

AbsoluteTime[] gives the number of seconds since the start of January 1, 1900. The value increases on every call, so the exact number you see will differ from the one above.