Here is my code :
{$M 16777216}
Program P1201_Which_day_is_it;
{$APPTYPE CONSOLE}
Var Days:array [1600..2400] of byte;
    fday,day,sum,month:byte;
    year:word;
    i,j,k,h,d,code:integer;
    s,t:string;
    Calendar:array[1..7] of string;
{-----------------------------------------------------------}
Procedure Init;
Begin
  Days[1600]:=2;
  i:=1601;
  While i<=year do
    Begin
      days[i]:=days[i-1];
      if (i-1) mod 4 =0 then inc(days[i]);
      if i-1=1918 then inc(days[i]);
      inc(days[i]);
      if days[i]>7 then days[i]:=days[i] mod 7;
      inc(i);
    end;
End;
{-----------------------------------------------------------}
Begin
 {$IFNDEF ONLINE_JUDGE}
 Assign(input,'Input.txt'); Reset(input);
 Assign(output,'Output.txt'); Rewrite(output);
 {$ENDIF}
 Readln(input,day,month,year);
 init; fday:=days[year];
 For i:=1 to month-1 do
   Begin
     if (i=1)or(i=3)or(i=5)or(i=7)or(i=8)or(i=10) then inc(fday,3);
     if (i=2) then
       if year mod 4 = 0 then inc(fday,1);
     if (i=4)or(i=6)or(i=9)or(i=11)or(i=12) then inc(fday,2);
   End;
 if (month=1)or(month=3)or(month=5)or(month=7)or(month=8)or(month=10) then
   sum:=31;
 if (month=2) then if (year mod 4=0) then sum:=29 else sum:=28;
 if (month=4)or(month=6)or(month=11)or(month=12) then sum:=30;
 Calendar[7]:='sun'; Calendar[1]:='mon'; Calendar[2]:='tue';
 Calendar[3]:='wed'; Calendar[4]:='thu'; Calendar[5]:='fri';
 Calendar[6]:='sat';
 if fday>7 then fday:=fday mod 7;
 for i:=fday-1 downto 1 do Calendar[i]:=Calendar[i]+'     ';
 k:=fday;
 for i:=1 to sum do
   begin
     if i=day then s:=']' else s:=' ';
     str(i,t); if length(t)=1 then t:=' '+t; s:=t+s;
     if i=day then s:='['+s;
     while length(s)<5 do s:=' '+s;
     Calendar[k]:=Calendar[k]+s;
     if k=7 then k:=1 else inc(k);
   end;
 For i:=1 to 7 do
   Begin
     While Calendar[i][length(calendar[i])]=' ' do
       delete(Calendar[i],Length(calendar[i]),1);
     writeln(output,Calendar[i]);
   End;
 {$IFNDEF ONLINE_JUDGE}
 Close(input);
 Close(output);
 {$ENDIF}
End.

My code have WA#6, but I think it alright !!

No 1918 or 1752 calendar corrections must be taken into account. Do just what is asked in the condition.