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SAS Tip of the Month
January 2015
(for SAS)

Dates and times are something programmers deal with every day. It is easy to see a date and/or time in character form, but how does SAS store that date in a numeric form?

To bring dates or times in character format, SAS has many ways that this can be done, but here are some examples:

   Date/Time Text     SAS Code
   12MAY2014          var=INPUT(text,DATE9.);
   12MAY14            var=INPUT(text,DATE7.);
   12/05/2014         var=INPUT(text,DDMMYY10.);
   05/12/2014         var=INPUT(text,MMDDYY10.);
   MAY2014            var=INPUT(text,MONYY7.); 
   2014-05-12         var=INPUT(text,YYMMDD10.);
   15:32              var=INPUT(text,TIME5.);
   12MAY2014:15:32.   var=INPUT(text,DATETIME15.);

The second parameter to the INPUT function is called an INFORMAT which tells SAS how to read the text – SAS has a load of them but the ones above are the most common for bringing in date and/or times from a text string.

Now how does SAS store these dates and times numerically?

For dates, “day 0” is January 1st, 1960 and has a value of zero. The date range that is possible in SAS is year 1582 to year 19,900. As the date is stored as a number it is easy to calculate durations, i.e. day number of one date minus the day number of another date.

For times, this is the number of seconds from mid-night, and has a range of 0 to 86,400 (there are 86,400 seconds in a day).

Lastly, a SAS datetime value is a value representing the number of seconds between January 1, 1960 and an hour/minute/second within a specified date.

However, knowing these numbers, it is impossible to see what date and/or time it is. Above we used INFORMATS to read the dates in, now we can display them using some formats:

   FORMAT Name   Display
   DATE9.        12MAY2014
   TIME5.        15:32 
   DATETIME15.   12MAY2014:15:32

Occasionally I will get a datetime variable but I just need the date portion for the program – this can be done using the DATEPART function as the following code illustrates:

   var = DATEPART(datetime_numeric_variable);

I hope this small introduction into the world of dates and times was useful.