%juliandate macro function

Astronomers use it and so too does the Google search daterange operator (e.g. daterange:2436900-2436934). The Julian calendar starts at noon universal time (UT), 1 January 4713 BCE (before current era or BC), which is before recorded history. In the business world, Julian date has represented the year and sequential day of that year, now known as an ordinal date. Ever since 1988, the ISO 8601 defines current Julian date usage as astronomers use it.

SAS uses the Gregorian calendar which starts on 15 October 1582 to take into account the inaccuracies of the Julian calendar. According to this article, the Gregorian calendar was developed as a refinement of the Julian calendar, shortening the average year by 0.0075 days to stop the drift of the calendar with respect to the equinoxes. To deal with the 10 days of accumulated drift, the date was advanced so that 4 October 1582 was followed by 15 October 1582.

Of course, SAS uses January 1, 1960 as its days zero (0) so adding 2436934.5 days creates the Julian date. SAS does not have any function to return the ISO 8601 or Julian date rather all Julian type functions from SAS relate to ordinal dates. And according to this SAS knowledge base link, "there are no plans to change the names or functionality" of the SAS functions, informats or formats related to Julian dates.

So if you ever need to obtain a Julian date, just use the below code. The Julian date for 14 August 2018 is 2458344.5.

%macro juliandate(date = %sysfunc(date()));
   %sysevalf(&date + 2436934.5)
%mend;