SAS date difference - sas

Question

what is wrong in below code
%let a='2017-01-01';
%let b='2017-12-01';
%let days = %sysfunc(intck(month,"&a"d,"&b"d));
%put days;
Below is the error
ERROR: Argument 2 to function INTCK referenced by the %SYSFUNC or %QSYSFUNC macro function is not a number.
ERROR: Argument 3 to function INTCK referenced by the %SYSFUNC or %QSYSFUNC macro function is not a number.
ERROR: Invalid arguments detected in %SYSCALL, %SYSFUNC, or %QSYSFUNC argument list. Execution of %SYSCALL statement or %SYSFUNC
or %QSYSFUNC function reference is terminated.
67 %put days;
days

Answer 1

Three problems:
Your dates are not SAS date literals. SAS date literals take the format of 'DDMMMYYYY'd or 'DDMMMYY'd For example, 01JAN2018'd, or 01JAN18'd.
You have put quotes around your macro variables that declare the dates, and put double-quotes around them a second time when calling intck.
An & needs to prefix days.
The below code addresses these problems:
%let a=01JAN2017;
%let b=01DEC2017;
%let months = %sysfunc(intck(month,"&a"d,"&b"d));
%put &months;
Because you are calculating the number of months between January 2017 and December 2017, I renamed your macro variable to months.

Answer 2

I guess you want to do this in explicit SQL pass through. for doing that you have to something like this and you can use Teradata specific functions.
/* define date as Teradata Understands*/
%let a= '2017-01-01';
%let b= '2017-12-01';
/* use either of solutions and I do not have Teradata handy, so I did
not explicitly checked this */
SELECT CAST(&b AS DATE) - CAST(&a AS DATE) MONTH(4);
select floor(MONTHS_BETWEEN(date &b - date &a));