/in/ex2.c: In function 'main':
/in/ex2.c:13:1: error: ISO C forbids nested functions [-Werror=pedantic]
 int firstday ()
 ^~~
/in/ex2.c:26:1: error: ISO C forbids nested functions [-Werror=pedantic]
 int numberofdays() { 
 ^~~
/in/ex2.c:38:16: error: unused variable 'lastday' [-Werror=unused-variable]
 int date=1, j, lastday=0, daynum= 0;
                ^~~~~~~
/in/ex2.c:38:13: error: unused variable 'j' [-Werror=unused-variable]
 int date=1, j, lastday=0, daynum= 0;
             ^
/in/ex2.c:8:6: error: unused variable 'month' [-Werror=unused-variable]
 char month[12][10] = {"Jan" , "February" , "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
      ^~~~~
/in/ex2.c:7:5: error: variable 'calendar' set but not used [-Werror=unused-but-set-variable]
 int calendar [5][7];
     ^~~~~~~~
/in/ex2.c: In function 'firstday':
/in/ex2.c:23:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
cc1: all warnings being treated as errors