topic Re: How to convert date to days in SAS Studio

How to convert date to days

sasuser123123 — Mon, 23 Dec 2019 10:20:37 GMT

Hello !

I've a variable 'date' which is numeric variable it contains date 29Dec08:10:00:00 so I need to convert into days. so how to convert this date to days . I'm wrote
Newdate=input(put (date,datetime18.), datetime18.),
But I got wrong numeric dates.. could you please solve this query..

Thank you.!
Regards..

Re: How to convert date to days

Kurt_Bremser — Mon, 23 Dec 2019 10:28:09 GMT

You do not have a date, you have a datetime. Datetimes are counts of seconds, dates are counts of days. To extract the date from a datetime, use the datepart() function.

Your double function call keeps the value as it is, only cutting off any fractions of seconds, which could be achieved easier with round().

Re: How to convert date to days

Shmuel — Mon, 23 Dec 2019 10:28:16 GMT

I don't know what you mean by converting a date into days,

but may be you mean:

date = datepart(datetime_variable);

Re: How to convert date to days

sasuser123123 — Mon, 23 Dec 2019 11:07:31 GMT

Thank you for suggestion, actually I'm trying to calculate age from two variables. While calculating age should we consider time and seconds or not

Re: How to convert date to days

Shmuel — Mon, 23 Dec 2019 11:41:14 GMT

having to variables you can calculate age by subtracting years:

age = intck('year', datetime2, datetime1);

age = intck('year', date2, date1);

Re: How to convert date to days

Kurt_Bremser — Mon, 23 Dec 2019 13:09:06 GMT

You have to use "dtyear" as the interval.

Re: How to convert date to days

ballardw — Mon, 23 Dec 2019 17:43:23 GMT

@sasuser123123 wrote:
Thank you for suggestion, actually I'm trying to calculate age from two variables. While calculating age should we consider time and seconds or not

That would be YOUR requirement to know.

Hours seldom become a consideration unless dealing with newborn babies though.

Re: How to convert date to days

JackHamilton — Mon, 23 Dec 2019 20:30:07 GMT

The code

age = intck('year', date2, date1);

will not always produce the result you might expect, because what it counts is the number of occurences of January 1 between the two dates:

 69         data _null_;
 70             years = intck('year', '31dec2019'd, '01jan2020'd);
 71             put years=;
 72         run;
 
 years=1

Use of the CONTINUOUS option might produce the result you want:

data _null_;
    years = intck('year', '31dec2019'd, '01jan2020'd, 'continuous');
    put years=;
run;

The traditional method of calculating age in SAS, attributed to Billy Kreuter, is

age =  floor(( intck( 'month', dob, death) - ( day(death) < day(dob)))/ 12);

<https://www.lexjansen.com/pharmasug/2011/CC/PharmaSUG-2011-CC20.pdf>

There's a lazy method that just takes the difference in days and divides by 365.25. Please don't use that method.

Re: How to convert date to days

ballardw — Mon, 23 Dec 2019 21:23:11 GMT

@Kurt_Bremser wrote:

You have to use "dtyear" as the interval.

Or DTDAY, DTMONTH , DTWEEK (see a pattern here?).