如何将最初为日期的序列号转换为该日期最初的天数？

Question

首先我有一个日期（格式：dd、mm、yyyy）例如：21、3、2012 并将其转换为序列号，在本例中为 40988。现在我想找到我的问题一种算法，returns 最初给定的天数，因此在示例中它将是 21。这是我用来将日期转换为序列号的代码：

      //intYears, intMonths, intDays are parameter variables
      var serial = 0

      //Going from 1900 to intYears - 1 (excluding the last year)
      var arrNormalYears = new Array()
      for (let i = 1900; i < intYears; i++) {
         arrNormalYears.push(i)
      }

      //Count the number of normal years excluding the 
      //parameter year (intYear)

      //the function numberOfDaysYear checks for us if the 
      //year is a leap year or a normal year

      var normalYears = 0
      for (let j = 0; j < arrNormalYears.length; j++) {
         if (numberOfDaysYear(arrNormalYears[j]) == 365) {
            normalYears += 1
         }
      }
      //multiply the count and add it to serial

      serial += normalYears * 365


      //Same process for leap years

      var arrLeapYears = new Array()

      for (let m = 1900; m < intYears; m++) {
         arrLeapYears.push(m)
      }

      //Count the number of leap years
      var leapYears = 0
      for (let a = 0; a < arrLeapYears.length; a++) {
         if (numberOfDaysYear(arrLeapYears[a]) == 366) {
            leapYears += 1
         }
      }

      serial += leapYears * 366


      //Now including the parameter variable intYear
      
      //Using the same process as above except this time 
      //its for the months

      var arrMonths = new Array()
      for (let k = 1; k < intMonths; k++) {
         arrMonths.push(k)
      }

      //Here the function numberOfDaysMonth gives us the 
      //number of days for the specific month, it also 
      //checks if it's a leap year 
      //also excluding the last month

      for (let x = 0; x < arrMonths.length; x++) {
         if (numberOfDaysMonth(arrMonths[x]) == 31) {
            serial += 31
         }
         else if (numberOfDaysMonth(arrMonths[x]) == 30) {
            serial += 30
         }
         else if (numberOfDaysMonth(arrMonths[x]) == 28) {
            serial += 28
         }
         else if (numberOfDaysMonth(arrMonths[x]) == 29) {
            serial += 29
         }
      }

      //Simply adding the days that are left
      serial += intDays

      return serial
   }

现在，通过了解我用于将日期转换为序列号的算法，我无法以某种方式反转算法和 return 上面代码中解释的日期。

Answer 1

您应该使用 setDate 和替换天数而不是像其他人所说的那样添加它。 JS Date 构造函数允许大于您通常认为允许的数字并给出正确的日期。

let serial = 40988;
let dayOfMonth = new Date(1900, 0, serial).getDate();
console.log(dayOfMonth);

更新

如果您将序列设置为零，您将得到 1899 年 12 月 31 日 - 您已经成功地重新创建了 OADate！原来都没注意到

注意

JavaScript 处理您当地时区的日期。只要您坚持使用单一时区 (local/UTC/whatever)，您应该没问题。

如何将最初为日期的序列号转换为该日期最初的天数？

How do I convert a serial number which was initially a date to the number of days that the date initially had?

javascript

algorithm