// Simple calculation of days between two dates based on time value
function getDaysDiff(start, end) {
return ((parseStringUTC(end) - parseStringUTC(start))/8.64e7).toFixed(2);
}
// Expects input in ISO8601 format: yyyy-mm-ddThh:mm:ss.sssZ
// Always expects UTC
function parseStringUTC(s) {
s = s.split(/D/);
s[6] = s[6]? ('0.'+ s[6]) * 1000 : 0;
return new Date(Date.UTC(s[0],--s[1],s[2],s[3]||0,s[4]||0,s[5]||0,s[6]||0));
}
/* Get the difference between two dates in years, months, days,
** hours, minutes and seconds.
**
** Difference is values to add to earlier date to reach later date.
**
** Does not consider daylight saving changes so may be incorrect by offset
** difference over daylight saving boundaries, so use UTC values (pass
** values as date.toISOString() or format like ISO 8601 UTC)
**
** @param {string} d0 - earlier date in format y-m-d h:m:s, can also be
** yyyy-mm-ddThh:mm:ssZ, the timezone offset is ignored
** the string is not validated
** @param {string} d1 - later date in same format as above. If d1 is earlier
** than d0, results are unreliable.
** @returns {Array} values for years, months, days, hours, minutes and
** seconds (milliseconds as decimal part of seconds)
*/
function dateDiff(d0,d1) {
var s = d0.split(/D/);
var e = d1.split(/D/);
// Calculate initial values for components,
// Time component is optional, missing values treated as zero
var ms = (e[6]||0) - (s[6]||0);
var sec = (e[5]||0) - (s[5]||0);
var min = (e[4]||0) - (s[4]||0);
var hr = (e[3]||0) - (s[3]||0);
var day = e[2] - s[2];
var mon = e[1] - s[1];
var yr = e[0] - s[0];
// Borrowing to resolve -ve values.
if (ms < 0) { // ms borrow from sec
ms += 1000;
--sec;
}
if (sec < 0) { // sec borrows from min
sec += 60;
--min;
}
if (min < 0) { // min borrows from hr
min += 60;
--hr;
}
if (hr < 0) { // hr borrows from day
hr += 24;
--day;
}
// Day borrows from month, a little complex but not too hard
if (day < 0) {
var prevMonLen = new Date(e[0], e[1]-1, 0).getDate();
// If the start date is less than the number of days in the previous month,
// set days to previous month length + current diff days value
// Note that current diff days may have had a day borrowed, so don't use end date - start date
// Otherwise, if the start date is equal to or greater than the number of
// days in the previous month, just set to end date. That's because adding
// 1 month to 30 Jan should be last day in Feb (i.e. 28 or 29), not 2 or 1 March
// respectively, which is what happens if adding 1 month to a Date object for 30 Jan.
// Similarly, 31 May + 1 month should be 30 June, not 1 July.
day = s[2] < prevMonLen? prevMonLen + day : +e[2];
--mon;
}
if (mon < 0) { // mon borrows from yr
mon += 12;
--yr;
}
// If days >= number of days in end month and end date is last day
// of month, zero mon and add one to month
// If then months = 12, zero and add one to years
var endMonLen = new Date(e[0], e[1], 0).getDate();
if (day >= endMonLen && s[2] > e[2] && e[2] == endMonLen) {
day = 0;
++mon;
if (mon == 12) {
mon = 0;
++yr;
}
}
return [yr,mon,day,hr,min,+(sec + '.' + ('00'+ms).slice(-3))];
}
/* Format output from dateDiff function, e.g. 3years, 2 days, 23.12 seconds
**
** @param {Array} v - values array in order years, months, days, hours, minutes
** seconds (milliseconds as decimal part of seconds)
** @returns {string} Values with their names appended. Adds "s" to values other
** than 1, zero values omitted, e.g. "0 months" not returned.
*/
function formatOutput(v) {
var values = ['year','month','day','hour','minute','second']
return v.reduce(function (s, x, i) {
s += x? (s.length? ' ' : '') +
(i == 5? x.toFixed(3) : x) + ' ' + values[i] + (x==1?'':'s'):'';
return s;
}, '');
}
// Tests, focus on February
var dates = [
['2016-01-31','2016-03-01'], // 1 month 1 day - 31 Jan + 1 month = 29 Feb
['2016-01-29','2016-03-01'], // 1 month 1 day - 29 Jan + 1 month = 29 Feb
['2016-01-27','2016-03-01'], // 1 month 3 days - 27 Jan + 1 month = 27 Feb
['2016-01-27','2016-03-29'], // 2 months 2 days - 27 Jan + 2 month = 27 Mar
['2016-01-29','2016-03-27'], // 1 month 27 days - 29 Jan + 1 month = 29 Feb
['2015-12-31','2016-01-30'], // 30 days - 31 Dec + 30 days = 30 Jan
['2015-12-27','2016-01-30'], // 1 month 3 days - 27 Dec + 1 month = 27 Jan
['2016-02-29','2017-02-28'], // 1 year could also be 11 months 30 days
// since 29 Feb + 11 months = 28 Feb, but 28 Feb is last day of month
// so roll over to full year
// Both work, but 1 year is more logical
['1957-12-04','2016-02-20'], // 58 years 2 months 16 days
['2000-02-29','2016-02-28'], // 15 years 11 months 30 days
// Not full year as Feb 2016 has 29 days
['2000-02-28','2016-02-28'], // 16 years
['2000-02-28','2016-02-29'], // 16 years 1 day
['2016-02-28T23:52:19.212Z','2016-12-02T01:48:57.102Z'] // 9 months 3 days 1 hour 56 minutes 37.899 seconds
];
var arr = [];
dates.forEach(function(a) {
arr.push(a[0] + ' to ' + a[1] + '<br>' + formatOutput(dateDiff(a[0], a[1])));
});
document.write(arr.join('<br>'));
table {
border-collapse:collapse;
border-left: 1px solid #bbbbbb;
border-top: 1px solid #bbbbbb;
}
input {
width: 12em;
}
input.bigGuy {
width: 32em;
}
td {
border-right: 1px solid #bbbbbb;
border-bottom: 1px solid #bbbbbb;
}
td:nth-child(1) { text-align: right; }
<form onsubmit="this.doCalc.onclick(); return false;">
<table>
<tr>
<td width="250"><label for="startDate">Start date (yyyy-mm-dd)</label>
<td><input name="startDate" id="startDate" value="2012-08-09T22:15:03.22" size="25">
<tr>
<td><label for="endDate">End date (yyyy-mm-dd)</label>
<td><input name="endDate" id="endDate" value="2013-08-13T12:10:03.22" size="25">
<tr>
<td><label for="dateDifference">Date difference: </label>
<td><input name="dateDifference" readonly class="bigGuy">
<tr>
<td><label for="daysDifference">Days difference: </label>
<td><input name="daysDifference" readonly>
<tr>
<td>
<input type="button" value="Calc date difference" name="doCalc2" onclick="
this.form.dateDifference.value = formatOutput(dateDiff(this.form.startDate.value, this.form.endDate.value));
this.form.daysDifference.value = getDaysDiff(this.form.startDate.value, this.form.endDate.value) + ' days';
">
<td><input type="reset">
</table>
</form>