その２４：グレゴリオ暦日付計算

．．．省略．．．

＜script＞

var Weeks = ["土", "日", "月", "火", "水", "木", "金"];

function calc() {
  var elm = document.getElementById('TXTY0');
  var y0 = Number(elm.value)
  elm = document.getElementById('TXTM0');
  var m0 = Number(elm.value)
  elm = document.getElementById('TXTD0');
  var d0 = Number(elm.value)
  elm = document.getElementById('TXTY1');
  var y1 = Number(elm.value)
  elm = document.getElementById('TXTM1');
  var m1 = Number(elm.value)
  elm = document.getElementById('TXTD1');
  var d1 = Number(elm.value)
  elm = document.getElementById('TXTDT');
  var dt = Number(elm.value)

  if(m0 == 1 || m0 == 2){
    y0--;
    m0 += 12;
  }
  var days0 = Math.floor((365*y0 + Math.floor(y0/4) - (Math.floor(y0/100) - Math.floor(y0/400)) + Math.floor(y0/1000) )+Math.floor(306*(m0+1)/10)+d0-429);
  var flg = false;
  var days1 = dt;
  if(0 ＜ y1){
    flg = true;
    if(m1 == 1 || m1 == 2){
      y1--;
      m1 += 12;
    }
    days1 = Math.floor((365*y1 + Math.floor(y1/4) - (Math.floor(y1/100) - Math.floor(y1/400)) + Math.floor(y1/1000) )+Math.floor(306*(m1+1)/10)+d1-429+dt) - days0;
  }
  else {
    y1 = y0;
    m1 = m0;
    d1 = d0;
  }

  var daya = days1 + days0;
  var weeka = daya % 7;
  var msa = (daya - days0) * 24 * 60 * 60 * 1000;

  elm = document.getElementById('TXTDTA');
  elm.value = daya - days0;
  elm = document.getElementById('TXTWKA');
  elm.value = Weeks[weeka];
  elm = document.getElementById('TXTMSA');
  elm.value = msa;

  var ya = Math.floor(((daya+428)*400)/146097);
  var x = (daya + 428) - Math.floor((ya * 146097) / 400) - Math.floor(ya/1000) + 2;
  if(x ＜ 123){
    ya--;
    x = (daya + 428) - Math.floor((ya * 146097) / 400) - Math.floor(ya/1000) + 2;
  }
  if(ya % 4 == 0){
    if(((ya % 100 == 0)&&(ya % 400 != 0))||(ya == 0));
    else x--;
  }

  var ma = Math.floor(10 * x / 306) - 1;
  var da = Math.floor(x - 306*(ma+1) / 10);
  if(da ＜= 0){
    ma--;
    da = Math.floor(x - 306*(ma+1) / 10);
  }
  if(12 ＜ ma) {
    ya++;
    ma -= 12;
  }

  elm = document.getElementById('TXTYA');
  elm.value = ya;
  elm = document.getElementById('TXTMA');
  elm.value = ma;
  elm = document.getElementById('TXTDA');
  elm.value = da;

}

＜/script＞

．．．省略．．．

＜hr＞
＜br＞
日付0＜br＞
西暦＜input type="text" id="TXTY0" value="1"＞年　＜input type="text" id="TXTM0" value="1"＞月　＜input type="text" id="TXTD0" value="1"＞日＜br＞
日付1＜br＞
西暦＜input type="text" id="TXTY1" value="-1"＞年　＜input type="text" id="TXTM1" value="-1"＞月　＜input type="text" id="TXTD1" value="-1"＞日＜br＞
加算日数＜input type="text" id="TXTDT" value="0"＞日＜br＞
＜br＞
解答＜br＞
西暦＜input type="text" id="TXTYA" value="1" disabled＞年　＜input type="text" id="TXTMA" value="1" disabled＞月　＜input type="text" id="TXTDA" value="1" disabled＞日＜br＞
日数＜input type="text" id="TXTDTA" value="0" disabled＞日＜br＞
曜日＜input type="text" id="TXTWKA" value="土" disabled＞曜日＜br＞
ミリ秒＜input type="text" id="TXTMSA" value="0" disabled＞ミリ秒＜br＞
＜br＞
＜input type="button" onclick="calc()"  value="計算"＞＜br＞
＜br＞
＜hr＞

．．．省略．．．