How can i change my code by using the mod command?

Any advice or help would be greatly appreciated.

%program dayofweek.m This program acceptes any day from this month 
%(April 2017) and returns the day of the week.
N=input('Enter a date for April 2017 to display the day of the week. ')
if N==0 
  disp('Enter a day that does not equal zero. ')
elseif N==2
  disp('Sunday')
elseif N==9
  disp('Sunday')
elseif N==16
  disp('Sunday')    
elseif N==23
  disp('Sunday')    
elseif N==30
  disp('Sunday')    
elseif N==3
  disp('Monday')
elseif N==10
  disp('Monday')
elseif N==17
  disp('Monday')
elseif N==24
  disp('Monday')    
elseif N==4
  disp('Tuesday')
elseif N==11
  disp('Tuesday')
elseif N==18
  disp('Tuesday')
elseif N==25
  disp('Tuesday')
elseif N==5
  disp('Wednesday')
elseif N==12
  disp('Wednesday')
elseif N==19
  disp('Wednesday')
elseif N==26
  disp('Wednesday')
elseif N==6
  disp('Thursday')
elseif N==13
  disp('Thursday')
elseif N==20
  disp('Thursday')
elseif N==27
  disp('Thursday')
elseif N==7
  disp('Friday')
elseif N==14
  disp('Friday')
elseif N==21
  disp('Friday')
elseif N==28
  disp('Friday')
elseif N==1
  disp('Saturday')
elseif N==8
  disp('Saturday')
elseif N==15
  disp('Saturday')
elseif N==22
  disp('Saturday')
elseif N==29
  disp('Saturday')
elseif N>30
 disp('The entered date does NOT exist. Please enter another date. ')
end

Answer 1

[dpb]

After your error checking all you need is

...
days={'Saturday','Sunday','Monday','Tuesday','Wednesday','Thursday','Friday'};
disp(days{mod(N,7}+1)

This is, of course, only valid for a month that begins on a Saturday; it would be more useful to use a more general routine.

NB: Unless this is homework, look at

doc weekday  % more general routine

Sure there are some other newer routines with the datetime class now, too, but haven't looked for just what might be the best in that vein...

Answer 2

[John D'Errico]

days = {'Friday', 'Saturday', 'Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday'};
days(mod(N,7) + 1)

Answer 3

[Shawn Marshall]

Thank you dpb and John D'Errico.