Language: C

n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}

Compiler output:
main.c:1:1: warning: data definition has no type or storage class
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      | ^
main.c:1:1: error: type defaults to 'int' in declaration of 'n' [-Wimplicit-int]
main.c:1:17: error: excess elements in 'int[]' initializer
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                 ^~~~~~~~
main.c:1:17: note: (near initialization for 'n')
main.c:1:26: error: excess elements in 'int[]' initializer
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                          ^~~~~~~~~~
main.c:1:26: note: (near initialization for 'n')
main.c:1:37: error: excess elements in 'int[]' initializer
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                     ^~~~~~~~
main.c:1:37: note: (near initialization for 'n')
main.c:1:46: error: excess elements in 'int[]' initializer
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                              ^~~~~~~~
main.c:1:46: note: (near initialization for 'n')
main.c:1:55: error: excess elements in 'int[]' initializer
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                                       ^~~~~~~~~
main.c:1:55: note: (near initialization for 'n')
main.c:1:65: error: excess elements in 'int[]' initializer
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                                                 ^~~~~~~~~~~
main.c:1:65: note: (near initialization for 'n')
main.c:1:5: error: cannot initialize array of 'int' from a string literal with type array of 'char'
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |     ^
main.c:1:78: error: type defaults to 'int' in declaration of 'm' [-Wimplicit-int]
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                                                              ^
main.c:1:80: error: type defaults to 'int' in declaration of 'd' [-Wimplicit-int]
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                                                                ^
main.c:1:82: error: return type defaults to 'int' [-Wimplicit-int]
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                                                                  ^~~~
main.c: In function 'main':
main.c:1:94: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                                                                              ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
main.c:1:94: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                                                                              ^~~~~
main.c:1:94: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:1:116: error: implicit declaration of function 'puts' [-Wimplicit-function-declaration]
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                                                                                                    ^~~~
main.c:1:116: note: include '<stdio.h>' or provide a declaration of 'puts'
main.c:1:122: error: passing argument 1 of 'puts' makes pointer from integer without a cast [-Wint-conversion]
    1 | n[]={"Thursday","Friday","Saturday","Sunday","Monday","Tuesday","Wednesday"},m,d;main(){for(;scanf("%d%d",&m,&d),m;puts(n[(d-13*~m/5)%7]))m<3?d-=2,m+=12:0;}
      |                                                                                                                         ~^~~~~~~~~~~~~~~
      |                                                                                                                          |
      |                                                                                                                          int
main.c:1:122: note: expected 'const char *' but argument is of type 'int'