Date Utilities in SAS

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Convert a Date to a String of the Format "YYYYMMDD"

data _null_;
    x = put("23Aug2014"d, yymmddn8.);
    put x date9.;
run;

or

data _null_;
    x = putn("23Aug2014"d, "yymmddn8.");
    put x date9.;
run;

Both of the 2 data steps print "20140823". The following is a comprehensive list of expressions (that can be used in data steps and procedures) to convert dates into strings with given formats. Let d be a numeric variable with the value 19958 (which represent Aug 23, 2014 in SAS).

A convenient way is to wrap these formats into functions with (better) meaningful names in the fcmp procedure for use.

Convert a string of the format "YYYYMMDD" to a Date

data _null_;
    x = input("20140823", yymmdd8.);
    put x date9.;
run;

or

data _null_;
    x = inputn("20140823", "yymmdd8.");
    put x date9.;
run;

Both of the 2 data steps print "23AUG2014", which menas that the string has been converted to a date successfully. The following is a comprehensive list of expressions (that can be used in data steps and procedures) to convert strings with valid formats into dates.

Notice that several interesting things I'd like to point out here.

1. For converting a string to date, all numeric informats (yymmddn8., mmddyyn8., ddmmyyn8., yymmddn6., mmddyyn6., ddmmyyn6., yymmn. and mmyyn.) and incomplete informats (yymm. and mmyy.) are invalid.

2. Both "20140823" and "14/08/23" use the informat yymmdd8. when converting to dates.

3. The informat names must NOT be quoted if you use the function input, while they must be quoted if you use the function inputn or inputc. The underlying difference is that input takes a compile-time informat, so there is no need to quote the informat and it is fixed. The function inputn/inputc takes a run-time informat, so you must quote the informat and it can be changed based on different contexts.

4. The function inputn converts a character value to a numeric one; takes numeric informat the function inputc converts a character value to a character value; takes character informat the function input converts a character value to a character/numeric one. character/numeric informat

5. SAS implicitly convert between numeric and character values ...

Create a Date From Year, Month and Day

data _null_;
    x = mdy(8, 23, 2014);
    put x date9.;
run;

Extract Year, Month or Day from a Date

data _null_;
    date = mdy(8, 23, 2014);
    y = year(date);
    m = month(date);
    d = day(date);
    put date date9.;
    put y;
    put m;
    put d;
run;

Notice that all the 3 functions year, month and day return numeric values.

Arithmatic Operations on Date

1. last day of the month in a given date

    d = intnx('month', d, 0, 'e');

convert between data and datetime

data _null_;
    d = '29FEB1984'd;
    put d date.;
    /* convert date to DateTime */
    dt = dhms(d,0,0,0);
    put dt datetime.;
    /* extract date from DateTime */
    d = datepart(dt);
    put d date.;
run;