How to convert date to days

[sasuser123123]

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..

[Kurt_Bremser]

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().

[Shmuel]

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

but may be you mean:

      date = datepart(datetime_variable);

[sasuser123123]

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

[Shmuel]

having to variables you can calculate age by subtracting years:

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

or

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

[Kurt_Bremser]

You have to use "dtyear" as the interval.

[ballardw]

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@Kurt_Bremser wrote:

You have to use "dtyear" as the interval.

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

[JackHamilton]

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.

[ballardw]

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@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

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That would be YOUR requirement to know.

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