OK, this is basically a Javascript version of How can I convert a decimal year value into a Date in Ruby? and not exactly a duplicate of Javascript function to convert decimal years value into years, months and days
Input:
2015.0596924
Desired output:
January 22, 2015
I have solved it (see below), but I expect (just like the Ruby version of this question) that there is a better way.
JavaScript will resolve the dates for you if you add too much time. See demonstration below. The solution below doesn't calculate the leap year based on the algorithm, but takes next year's date and subtracts it from this year. This assumes that the JavaScript specification properly calculates leap years.
See Mozilla Docs for more info.
function decimalDateToJsDate(time) { var year = Math.floor(time); var thisYear = new Date(year, 0, 1); var nextYear = new Date(year + 1, 0, 1); var millisecondsInYear = nextYear.getTime() - thisYear.getTime(); var deltaTime = Math.ceil((time - year) * millisecondsInYear); thisYear.setMilliseconds(deltaTime); return thisYear; } document.getElementById("output").innerHTML = decimalDateToJsDate(2015.0596924);
<pre id="output"></pre>
The other solution would be:
date
for given year (integer part) In script:
function leapYear(year) { return ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0); }; function convertDecimalDate(decimalDate) { var year = parseInt(decimalDate); var reminder = decimalDate - year; var daysPerYear = leapYear(year) ? 366 : 365; var miliseconds = reminder * daysPerYear * 24 * 60 * 60 * 1000; var yearDate = new Date(year, 0, 1); return new Date(yearDate.getTime() + miliseconds); } var date = convertDecimalDate(2015.0596924); console.log(date);
You can play with it on this Fiddle .
function leapYear (year){
return ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0);
}
function getMonthAndDayFromDayOfYear(dayOfYear, year){
var daysInMonthArray = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
if (leapYear(year)) { daysInMonthArray[2] = 29; }
var daysLeft = dayOfYear;
var month = 0;
for (i=0; i<daysInMonthArray.length; i++) {
var daysInThisMonth = daysInMonthArray[i];
if (daysLeft > daysInThisMonth) {
month += 1;
daysLeft -= daysInThisMonth;
} else {
break;
}
}
return { month: month, day: daysLeft };
}
function convertDecimalDate(decimalDate){
decimalDate = parseFloat(decimalDate);
var year = parseInt(decimalDate); // Get just the integer part for the year
var daysPerYear = leapYear(year) ? 366 : 365; // Set days per year based on leap year or not
var decimalYear = decimalDate - year; // A decimal representing portion of the year left
var dayOfYear = Math.ceil(decimalYear * daysPerYear); // day of Year: 1 to 355 (or 366)
var md = getMonthAndDayFromDayOfYear(dayOfYear, year);
var day = md['day'];
var month = md['month'];
return new Date(year,month,day);
}
var date = convertDecimalDate(2015.0596924);
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