When using ISO time informat B8601TM without an explicit length specification, SAS may use the characters in memory following the variable as part of the input.

To replicate:
• specify character variable with length $6
• specify second character variable with length $2
• specify informat without length (B8601TM.), default length is 8 in documentation.

The result is:

   NOTE: Invalid argument to function INPUT

The workaround is to specify explicit length when using informat to match the length of the input variable: B8601TM6.

Operating System and Release Information

/* specify character variable with length $6 
   specify second character variable with length $2 
   specify informat without length
   See Invalid argument to function INPUT  message 
*/

data one;
  x='123456';
  pm = 'xx';
  t = input(x,b8601tm.);
  put t time.;
run;

/* specify character variable with length $6 
   specify second character variable with length $2 
   specify informat with length of 6
   No Invalid argument message 
*/
data two;
  x='123456';
  pm = 'xx';
  t = input(x,b8601tm6.);
  put t time.;
run;

/* specify character variable with length $6 
   specify second character variable with length $2
     containing valid characters 
   specify informat without length
   No Invalid argument message 
*/
data three;
  x='123456';
  pm = '00';
  t = input(x,b8601tm.);
  put t time.;
run;

2    
3    /* specify character variable with length $6
4       specify second character variable with length $2
5       specify informat without length
6       See Invalid argument to function INPUT  message
7    */
8    
9    data one;
10     x='123456';
11     pm = 'xx';
12     t = input(x,b8601tm.);
13     put t time.;
14   run;

NOTE: Invalid argument to function INPUT at line 12 column 7.
       .
x=123456 pm=xx t=. _ERROR_=1 _N_=1
NOTE: Mathematical operations could not be performed at the following places. The results 
      of the operations have been set to missing values.
      Each place is given by: (Number of times) at (Line):(Column).
      1 at 12:7   
NOTE: The data set WORK.ONE has 1 observations and 3 variables.
NOTE: DATA statement used (Total process time):
      real time           0.07 seconds
      cpu time            0.04 seconds
      

15   
16   /* specify character variable with length $6
17      specify second character variable with length $2
18      specify informat with length of 6
19      No Invalid argument message
20   */
21   data two;
22     x='123456';
23     pm = 'xx';
24     t = input(x,b8601tm6.);
25     put t time.;
26   run;

12:34:56
NOTE: The data set WORK.TWO has 1 observations and 3 variables.
NOTE: DATA statement used (Total process time):
      real time           0.00 seconds
      cpu time            0.00 seconds
      

27   
28   /* specify character variable with length $6
29      specify second character variable with length $2
30        containing valid characters
31      specify informat without length
32      No Invalid argument message
33   */
34   data three;
35     x='123456';
36     pm = '00';
37     t = input(x,b8601tm.);
38     put t time.;
39   run;

12:34:56
NOTE: The data set WORK.THREE has 1 observations and 3 variables.
NOTE: DATA statement used (Total process time):
      real time           0.00 seconds
      cpu time            0.00 seconds