Is it possible to convert dates, like e.g.

date = "2018-02-15";

to be represented by whole number increments starting with 30 December 1899, midnight UTC? I believe this is called DATE format in Windows. Maybe there is an internal Mathematica function that does this?

  • $\begingroup$ hoe about DateObject[{2018, 02, 15}] $\endgroup$
    – ZaMoC
    Oct 18, 2018 at 14:48
  • $\begingroup$ @J42161217 Sorry, this does not return an integer number of days since 30 December 1899... $\endgroup$
    – Kagaratsch
    Oct 18, 2018 at 14:52
  • 3
    $\begingroup$ You could simply use AbsoluteTime[<date>] or DayCount["12/30/1899", "02/15/2018"] $\endgroup$
    – user42582
    Oct 18, 2018 at 15:01

2 Answers 2


Easiest way to avoid the units system would be something like

(AbsoluteTime["2018-02-15"] - AbsoluteTime["1899-12-30"])/86400

(untested, as I am on gedanken Mathematica)


So far I have hacked together the following:

  DateDifference[{1899, 12, 30, 0, 0, 0.`}, 
   DateList[ date ]]] // Round


Can this be made quicker, to be used with large sets of dates efficiently?


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