/* --------------------------------------------------------
	year-calc.js
	Version 1.1
	19 June 2007
	Original code by Don Whysall, copied by Ken Elmer
	
	coded to calculate dates in the Christian Year
------------------------------------------------------------ */

function set_array()
{
  months[0]="Jan"; months[1]="Feb"; months[2]="Mar"; months[3]="Apr"
  months[4]="May"; months[5]="Jun"; months[6]="Jul"; months[7]="Aug"
  months[8]="Sep"; months[9]="Oct"; months[10]="Nov"; months[11]="Dec"
  day_arr[0]="Sunday"; day_arr[1]="Monday"; day_arr[2]="Tuesday"; day_arr[3]="Wednesday"
  day_arr[4]="Thursday"; day_arr[5]="Friday"; day_arr[6]="Saturday"
  adv_arr[1]="Dec 3"; adv_arr[2]="Dec 2"; adv_arr[3]="Dec 1"; adv_arr[4]="Nov 30"
  adv_arr[5]="Nov 29"; adv_arr[6]="Nov 28"; adv_arr[0]="Nov 27"
}

   function do_calcs(year)
{
   var e_year=year-1900
   var a_ans=e_year%19
   var s_ans=(7*a_ans+1)/19
   s_ans=Math.round(s_ans-0.5)
   var t_ans=(11*a_ans+4-s_ans)%29
   var ex_year=e_year/4
   ex_year=Math.round(ex_year-0.5)
   var r_ans=(e_year+ex_year+31-t_ans)%7
   var e_ans=25-t_ans-r_ans
   e_ans=e_ans+8
   if(e_ans<9)
   {
     mon="Mar "
     dayn=e_ans+23
   }
   else
   {
     mon="Apr "
     dayn=e_ans-8
   }
   return mon+dayn
}

   function do_display(input_form,easter)
   {
      input_form.easter.value=easter
      eastdate=Date.parse(dayn+" "+mon+" "+year+" 12:00")
      ashwed=new Date(eastdate-46*days)
      out1=ashwed.getDate()
      out2=ashwed.getMonth()
      input_form.Ashw.value=months[out2]+" "+out1

      gfri=new Date(eastdate-2*days)
      out1=gfri.getDate()
      out2=gfri.getMonth()
      input_form.gfri.value=months[out2]+" "+out1

      ascd=new Date(eastdate+39*days)
      out1=ascd.getDate()
      out2=ascd.getMonth()
      input_form.ascd.value=months[out2]+" "+out1

      pent=new Date(eastdate+49*days)
      out1=pent.getDate()
      out2=pent.getMonth()
      input_form.pent.value=months[out2]+" "+out1

      xmas=new Date("25 Dec" +year+" 12:00")
      xmasd=xmas.getDay()
      input_form.xmas.value=day_arr[xmasd]

      advent=adv_arr[xmasd]
      input_form.advs.value=advent

   }

   function get_Easter(input_form)
   {
      year=parseFloat(input_form.year.value)
      if(year>max) {year=max}
      if(year<min) {year=min}
      input_form.year.value=year
      easter=do_calcs(year)
      do_display(input_form,easter)
   }

   function increment(input_form)
   {
      year=parseFloat(input_form.year.value)
      year+=1
      if(year>max) {year=max}
      if(year<min) {year=min}
      input_form.year.value=year
      easter=do_calcs(year)
      do_display(input_form,easter)
   }

   function decrement(input_form)
   {
      year=parseFloat(input_form.year.value)
      year-=1
      if(year<min) {year=min}
      if(year>max) {year=max}
      input_form.year.value=year
      easter=do_calcs(year)
      do_display(input_form,easter)
   }