How to Define date format from a given date - date

Question

I wanted to know, how can we define date format from given date
for example, i have date 20180423 then in sas I want to define format as 'yyyymmdd'
similarly , i have date given in data as 12022018 then i want to define as 'ddmmyyyy'
Please note that, date is provided to me in proper date, but i want to define format now.
Date given may be different in future
so I need to take care all of the date format through SAS
What I thought was given date 20180422
use substr function
data test;
a=20180422;
a=substr(a,1,4);
b=substr(a,5,1);
c=substr(a,7,1);
run;
but not sure.
If anyone can provide the solution,then it really helps me in my project work.
Thanks in Advance for help.

Answer 1

It sounds like you want to convert various values to a date. SAS stores dates as a number, being the number of days since 1st Jan 1960. It's then usual to format this number to display as a date, in whichever format is preferred.
When importing dates that's are already in a format, it is necessary to use the input function, along with an informat, to convert the formatted value to a SAS date. If the date values being read in are all in the same format, then the specific informat can be used. In your case, where different formats are used, you can use the anydtdte. informat which will convert most of the standard date formats to a SAS date.
The example below converts 3 different date formats to a SAS date, then displays the SAS date in the date9. format. I've printed both the unformatted and formatted new values to the log, just so you can see they are stored as numbers.
data _null_;
input date_in $20.;
date_out = input(date_in, anydtdte20.);
put date_in date_out date_out :date9.;
datalines;
20180422
12022018
27apr2018
;
run;

Answer 2

Use the input(a,anydtdte20.); this will convert any date to SAS date, then use the functions Year(), Month(), Day() to extract the data you want.
You will find this SAS Post very useful about dates and locales.
Solution:
I created a table with two rows; each row have a different date format YYYYMMDD & DDMMYYYY to show you how the code will handles different date formats, saved them to SAS date and broke them down to Year, Month & Day:
options DATESTYLE=DMY;
data have;
input a;
datalines;
20180422
12022018
;
run;
data test;
set have;
format date_a date9.;
date_a=input(a,anydtdte20.);
Year_a=year(date_a);
month_a=month(date_a);
day_a=day(date_a);
run;
Output:
a=20180422 date_a=22APR2018 Year_a=2018 month_a=4 day_a=22
a=12022018 date_a=12FEB2018 Year_a=2018 month_a=2 day_a=12

Answer 3

You can use an if condition inside a data step. Using If condition, check for the condition to be true (check date value satisfies the required criteria), then format the date using a put function.Put function can take a source as first argument and format as second argument , and return the formatted value. Different values of same column, can have different formats specified that way.
Something like this,
if a = 'date1CheckCondtion' then newA = put(a , dateformat1.);
if a = 'date2' then newA = put(a , dateformat2.);
You may then choose to get all values in a common format like this:
dateA=input(newA,mmddyy6.);