d_u_m(31,januar,_).
d_u_m(31,mart,_).
d_u_m(30,april,_).
d_u_m(31,maj,_).
d_u_m(30,jun,_).
d_u_m(31,jul,_).
d_u_m(31,avgust,_).
d_u_m(30,septembar,_).
d_u_m(31,oktobar,_).
d_u_m(30,novembar,_).
d_u_m(31,decembar,_).

d_u_m(28,februar,G):-not(prestupna(G)).
d_u_m(29,februar,G):-prestupna(G).

prestupna(G):-G mod 400=:=0.
prestupna(G):-G mod 4=:=0,G mod 100\=0.

program:- write('uneste mesec:'),read(X),write('unesite godinu:'),read(Y),
	  d_u_m(Z,X,Y),
	  write( 'mesec '),write(X),write( 'godina '),write(Y),write(' ima '),
          write(Z),write('dana').

/* Poziva se sa: program. */