clock - Modulo algorithm proving elusive -

i have color-wheel maps color each hour on 24-hour clock. given hour of day, want map colors 12-hour clock such colors 5 hours before , 6 hours after current hour used. gets bit tricky b/c 0th index of result has 0th color or 12th color of 24 color-wheel.

for example, given colors24 array of 24 colors , hour time of 5 final color12 array map colors24's indexes as:

{0,1,2,3,4,5,6,7,8,9,10,11} 

if hour 3, then:

{0,1,2,3,4,5,6,7,8,9,22,23} 

and if hour 9, then:

{12,13,14,15,4,5,6,7,8,9,10,11} 

bonus points if algorithm can generalized 2 arrays regardless of size long first evenly divisible second.

if hours total number of hours (24), length number of colors displayed @ time (12), , hour current hour, generic algorithm indexes color array:

result = []; add = hour + hours - (length / 2) - (length % 2) + 1; (i = 0; < length; i++) {     result[(add + i) % length] = (add + i) % hours; } 

here javascript implementation (generic, can used other ranges 24/12):

function getcolorindexes(hour, hours, length) {      var i, result, add;        if (hours % length) throw "number of hours must multiple of length";      result = [];      add = hour + hours - (length / 2) - (length % 2) + 1;      (i = 0; < length; i++) {          result[(add + i) % length] = (add + i) % hours;      }      return result;  }    console.log ('hour=3: ' + getcolorindexes(3, 24, 12));  console.log ('hour=5: ' + getcolorindexes(5, 24, 12));  console.log ('hour=9: ' + getcolorindexes(9, 24, 12));  console.log ('hour=23: ' + getcolorindexes(23, 24, 12));

as stated in question, number of hours (24) must multiple of length of array return.