在Javascript中OADate到毫秒时间戳

Question

我尝试做的恰恰相反:

什么相当于javascript中的DateTime.ToOADate()？

从OADate创建一个毫秒日期(自1970年1月1日以来的毫秒数)(1899年12月30日以来的天数作为双值)

我的猜测是我可以这样做:

this.unixTimeStampFromOADate = function( OADateFloat)
{
        var oaDateFor1970 = ?? ; //what's the value for 1/1/1970 in OADate format ?
        var delta = Math.floor(OADateFloat - oaDateFor1970);

        return delta*(1000*60*60*24); 
}

所以,如果我是对的,我需要OADate格式的1/1/1970的值.如果我错了,请你建议另一种转换方法吗？

Answer 1

Javascript日期使用自1970-01-01T00:00:00Z以来的毫秒时间值.日期1899-12-30的时间值是-2209197600000.

为了获得从那时起的日子,在今天开始时获取午夜的毫秒数,从OA纪元中减去它,在一天内除以ms并得到绝对值.请注意,时间值都是UTC,因此考虑了夏令时,闰年等.

var epoch = new Date(1899, 11, 30); // 1899-12-30T00:00:00
var now = new Date();               // 2013-03-22T<current time>
now.setHours(0,0,0,0)               // 2013-03-22T00:00:00

var oaDate  = Math.abs((epoch - now) / 8.64e7); // 41355 for 2013-03-22

您可以在此处针对某些日期对其进行测试(请注意,这些日期采用令人困惑的美国m/d/yy格式).

编辑

对不起,后退了.以下是一些双向功能.

还花了一些时间来解决它所说的"OLE自动化日期被实现为一个浮点数,其积分分量是1899年12月30日午夜之前或之后的天数"实际意味着在1899-12-30之间或之后00:00:00并且"小数部分代表当天的时间除以24".换句话说,当1899-12-29 00:00:00为-1时,`899-12-29 06:00:00的值为-1.25,而不是-0.75.

无论如何,这些功能现在似乎都有效,但请彻底测试:

var toOADate = (function () {
  var epoch = new Date(1899,11,30);
  var msPerDay = 8.64e7;

  return function(d) {
    var v = -1 * (epoch - d)/msPerDay;

    // Deal with dates prior to 1899-12-30 00:00:00
    var dec = v - Math.floor(v);

    if (v < 0 && dec) {
      v = Math.floor(v) - dec;
    }

    return v;
  }
}());


var fromOADate = (function() {
  var epoch = new Date(1899,11,30);
  var msPerDay = 8.64e7;

  return function(n) {
    // Deal with -ve values
    var dec = n - Math.floor(n);

    if (n < 0 && dec) {
      n = Math.floor(n) - dec;
    }

    return new Date(n*msPerDay + +epoch);
  }
}());

var now = new Date();
var oaNow = toOADate(now);
var now2 = fromOADate(oaNow);

alert('Today: ' + now + '\nOADate: ' + oaNow + '\noaNow to Date: ' + now2);

OADate的规范令人困惑,尤其是负数的处理方式.

编辑2019年2月

更新版本的函数,使用本地日期值.

/* Convert a Microsoft OADate to ECMAScript Date
** Treat all values as local.
** @param {string|number} oaDate - OADate value
** @returns {Date}
*/
function dateFromOADate (oaDate) {
  // Treat integer part is whole days
  var days = parseInt(oaDate);
  // Treat decimal part as part of 24hr day, always +ve
  var ms = Math.abs((oaDate - days) * 8.64e7);
  // Add days and add ms
  return new Date(1899, 11, 30 + days, 0, 0, 0, ms);
}


/* Convert an ECMAScript Date to a Microsoft OADate
** Treat all dates as local.
** @param {Date} date - Date to convert
** @returns {Date}
*/
function dateToOADate (date) {
  var temp = new Date(date);
  // Set temp to start of day and get whole days between dates,
  var days = Math.round((temp.setHours(0,0,0,0) - new Date(1899, 11, 30)) / 8.64e7);
  // Get decimal part of day, OADate always assumes 24 hours in day
  var partDay = (Math.abs((date - temp) % 8.64e7) / 8.64e7).toFixed(10);
  return days + partDay.substr(1);
}

var now = new Date();
var x = dateToOADate(now);
console.log('Now: ' + now.toString());
console.log('As an OADate: ' + x);
console.log('Back to date: ' + dateFromOADate(x).toString());

window.onload = function(){ 
  var el = document.getElementById('in')
  el.addEventListener('change', function() {
    var oaDate = dateToOADate(new Date(new Date(el.value)));
    document.getElementById('out').value = oaDate;
    document.getElementById('out2').value = dateFromOADate(oaDate);
  });
}