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Javascript to count the number of days for a specific month between two dates [duplicate]

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How to calculate number of days between two dates?
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I am new to javascript.
I have specific month columns (9/30/2022, 10/31/2022,11/30/2022). I have a contract with a start date and end date (spanning multiple months).
I need to determine the number of days the contract was active for a specific month column.
Example:
Contact Start Date: 09/15/2022
Contract End Date: 10/24/2022
Number of days the contract was active in Sept 2022 is 16.
I found the code below that gives me the contract period broken down for each month (i.e.) **9 - 17; 10 - 23; **
Thank you in advance for any assistance.
I found this code
function getDays() {
var dropdt = new Date(document.getElementById("arr").value);
var pickdt = new Date(document.getElementById("dep").value);
var result = "";
for (var year = dropdt.getFullYear(); year <= pickdt.getFullYear(); year++) {
var firstMonth = (year == dropdt.getFullYear()) ? dropdt.getMonth() : 0;
var lastMonth = (year == pickdt.getFullYear()) ? pickdt.getMonth() : 11;
for (var month = firstMonth; month <= lastMonth; month++) {
var firstDay = (year === dropdt.getFullYear() && month === firstMonth) ? dropdt.getDate() : 1;
var lastDay = (year === pickdt.getFullYear() && month === lastMonth) ? pickdt.getDate() : 0;
var lastDateMonth = (lastDay === 0) ? (month + 1) : month
var firstDate = new Date(year, month, firstDay);
var lastDate = new Date(year, lastDateMonth, lastDay);
result += (month + 1) + " - " + parseInt((lastDate - firstDate) / (24 * 3600 * 1000) + 1) + "; ";
}
}
return result;
}
function cal() {
if (document.getElementById("dep")) {
document.getElementById("number-of-dates").value = getDays();
}
Calculate
`

The following snippet will generate an object res with the keys being zero-based month-indexes ("8" is for September, "9" for October, etc.) and the values are the number of days for each of these months:
const start=new Date("2022-09-15");
const end=new Date("2022-11-24");
let nextFirst=new Date(start.getTime()), month, days={};
do {
month=nextFirst.getMonth();
nextFirst.setMonth(month+1);nextFirst.setDate(1);
days[month]=Math.round(((nextFirst<end?nextFirst:end)-start)/86400000);
start.setTime(nextFirst.getTime());
} while(nextFirst<end)
console.log(days);
This can be extended into a more reliable function returning a year-month combination:
function daysPerMonth(start,end){
let nextFirst=new Date(start.getTime()), year, month, days={};
do {
year=nextFirst.getFullYear();
month=nextFirst.getMonth();
nextFirst.setMonth(month+1);nextFirst.setDate(1);
days[`${year}-${String(1+month).padStart(2,"0")}`]=Math.round(((nextFirst<end?nextFirst:end)-start)/86400000);
start.setTime(nextFirst.getTime());
} while(nextFirst<end)
return days;
}
[["2022-09-15","2022-11-24"],["2022-11-29","2023-02-04"]].forEach(([a,b])=>
console.log(daysPerMonth(new Date(a),new Date(b))));

Managing and calculating dates, times, and date-times are notoriously finicky in javascript and across browsers. Rather than trying to define your own logic for this use the famous Moment.js library.
In particular to calculate the length between two dates you can utilize the diff function between two moments
var a = moment([2007, 0, 29]);
var b = moment([2007, 0, 25]);
var diff = a.diff(b, 'days') // 1
console.log(diff);
<script src="https://momentjs.com/downloads/moment.js"></script>
The supported measurements are years, months, weeks, days, hours, minutes, and seconds.

Calculate days between two dates once checkbox is checked

I am using below code which will count total days if cb1 is checked.
If cb1 is unchecked (default state) weekends will be excluded.
My 1st problem is that it is showing one day less in calculation once cb1 is checked and 2nd problem is that when cb1 is unchecked it is not showing any result.
Any help, please. I took reference from this thread.
(function () {
if (getField("cb1").value != "Off") {
var Start = this.getField("LeaveFrom").value;
var End = this.getField("LeaveEnd").value;
var dStart = util.scand("dd/mm/yyyy H:MM:SS", Start + " 0:00:00");
var dEnd = util.scand("dd/mm/yyyy H:MM:SS", End + " 0:00:00");
var diff = dEnd.getTime() - dStart.getTime();
var oneDay = 24 * 60 * 60 * 1000;
var days = Math.floor(diff/oneDay);
event.value = days;
} else {
var start = this.getField("LeaveFrom").value; // get the start date value
var end = this.getField("LeaveEnd").value; // get the end date value
var start =util.scand("dd/mm/yyyy H:MM:SS", start + " 0:00:00");
var end = util.scand("dd/mm/yyyy H:MM:SS", end + " 0:00:00");
event.value = dateDifference(start, end);
function dateDifference(start, end) {
if (end < start) return -1;
// Copy date objects so don't modify originals
var s = new Date(+start);
var e = new Date(+end);
// Get the difference in whole days
var totalDays = Math.round((e - s) / 8.64e7);
// Get the difference in whole weeks
var wholeWeeks = totalDays / 7 | 0;
// Estimate business days as number of whole weeks * 5
var days = wholeWeeks * 5;
// If not even number of weeks, calc remaining weekend days
if (totalDays % 7) {
s.setDate(s.getDate() + wholeWeeks * 7);
while (s < e) {
s.setDate(s.getDate() + 1);
// If day isn't a Friday or Saturday, add to business days
if (s.getDay() != 5 && s.getDay() != 6) {
++days;
}
}
}
return days;
}
}
})();

Increase number twice a week

How would you increase a a number on a webpage twice a week on specific days and times?
For example the webpage would read:
"2 Apples"
However every Tuesday & Thursday at 9:00pm the number should increase by two.
So by Friday the number should have increased to 6 "Apples"
What's a simple way to increment this in Javascript, php or Jquery?

As it was mentionned in the comments, I advise you to use a cron to handle this.
First, you have to store your value somewhere (file, databse, ...). Then, you should create a cron job, that runs a code that increase and update your value at the given days of the week.
Some help about crons : https://en.wikipedia.org/wiki/Cron#Examples
I would add this post about cron and php : Executing a PHP script with a CRON Job
Hope it helps

Here a Javascript version, you can pass it the date it should start counting, the date you want to know the ammount of apples of, the days of the week apples will be added, the hours of the day the updat will take place and the ammount of apples that will be added on each of these dates.
Date.prototype.addDays = function (days) {
var result = new Date(this);
result.setDate(result.getDate() + days);
return result;
}
Date.prototype.addHours = function (hours) {
var result = new Date(this);
result.setHours(result.getHours() + hours);
return result;
}
function getApples(startdate, date, updateDays, updateTime, applesPerUpdate) {
var startDay = startdate.getDay();
var firstUpdateDate;
for(day of updateDays) {
if (day >= startDay) {//assumes startdate has no time added
firstUpdateDate = startdate.addDays(day - startDay).addHours(updateTime);
break;
}
}
if (!firstUpdateDate)
firstUpdateDate = startdate.addDays(7 - (startDay - updateDays[0])).addHours(updateTime);
var updateDaysReverse = updateDays.slice(0).reverse();//clones the array
var dateDay = date.getDay();
var lastUpdateDate;
for(day of updateDaysReverse) {
if (day < dateDay || day == dateDay && date.getHours() > updateTime) {
lastUpdateDate = date.addDays(day - dateDay);
break;
}
}
if (!lastUpdateDate)
lastUpdateDate = date.addDays(updateDaysReverse[0] - (7 + dateDay));
lastUpdateDate = new Date(Date.UTC(1900 + lastUpdateDate.getYear(), lastUpdateDate.getMonth(), lastUpdateDate.getDate(), updateTime, 0, 0, 0));
var secs = Math.trunc((lastUpdateDate - firstUpdateDate));
if (secs < 0) return 0;
var dayDiffs = [];
for(day of updateDays)
dayDiffs.push(day - updateDays[0]);
var weeks = Math.trunc(secs / 604800000);
var days = Math.trunc((secs % 604800000) / 86400000);
var apples = weeks * updateDays.length;
for(diff of dayDiffs)
{
if (diff <= days)
apples++;
else
break;
}
return apples * applesPerUpdate;
}
// important, day and month is zero-based
var startDate = new Date(Date.UTC(2016, 01, 07, 0, 0, 0, 0));
var updateDays = [2, 4];// 0 = sunday , have to be in order and must be 0 <= x < 7
var updateTime = 9;
console.log(getApples(startDate, new Date(), updateDays, updateTime, 2));
Was more coplicated than I thaught, and i havn't testet it much, so there may be bugs.
Here is a plunker to play with the values.

total number of sundays in a month

I am using following code to determine total number of sundays in a month, however it gives incorrect result
function sundaysInMonth(start) {
var dat = new Date('1 ' + start);
var y = dat.getFullYear();
var m = dat.getMonth() + 1;
var days = new Date( y,m,0 ).getDate();
var sundays = [ 8 - (new Date( m + '/01/' + y ).getDay()) ];
for ( var i = sundays[0] + 7; i < days; i += 7 ) {
sundays.push( i );
}
return sundays.length;
}
When I call above functions like console.log(sundaysInMonth('September 2013')); then it returns 4 whereas September 2013 has 5 sundays.
I am getting above code from this post

Loops are not needed for this calculation.
function sundaysInMonth(start) {
var d = new Date('1 ' + start); // May not parse in all browsers
var ndays = new Date( d.getFullYear(), d.getMonth()+1, 0 ).getDate();
return Math.floor((ndays + (d.getDay() + 6) % 7) / 7);
}
Test for all months in 2013: http://jsfiddle.net/rGN28/2/

Aw, Matt beat me by one minute! I came up with basically the same solution, only with more comments. ;)
function sundaysInMonth(sMonthAndYear) {
// Get the year and month as integers
var dDate = new Date('1 ' + sMonthAndYear);
var y = dDate.getFullYear();
var m = dDate.getMonth() + 1;
// Get the number of days in the month
var iDayCount = new Date( y,m,0 ).getDate();
// Find the first Sunday
var iFirstSunday = (8 - dDate.getDay());
if (iFirstSunday > 7) {iFirstSunday = 1};
// Calculate the total number of Sundays in the month
var iSundayCount = Math.ceil ((iDayCount + 1 - iFirstSunday) / 7);
// Return the count
return iSundayCount;
}

Check this. I just fixed issue in your code
function sundaysInMonth(start) {
var dat = new Date('1 ' + start);
var y = dat.getFullYear();
var m = dat.getMonth() + 1;
var days = new Date( y,m,0 ).getDate();
var sundays = [ (8 - (new Date( m + '/01/' + y ).getDay())) % 7 ];
for ( var i = sundays[0] + 7; i < days; i += 7 ) {
sundays.push( i );
}
return sundays.length;
}
In array variable sundays we need to intially store the first day value which is a sunday. There was a small bug for months with Day 1 is sunday. For example as in your question September 2013
For these months your code will store 8 instead of 1 sundays array as first sunday. I fixed it

Although the question is old but here is my attempt to find number of Sundays in a month if anyone needs help.
<?php
$year = 2020; // Year to check
$month = 1; // Month to check (1-12)
// Get the first and last day of the month as timestamps
$firstDay = strtotime("{$year}-{$month}-01");
$lastDay = strtotime("+1 month", $firstDay);
// Initialize a counter variable
$numSundays = 0;
// Loop through each day of the month
for ($i = $firstDay; $i < $lastDay; $i = strtotime("+1 day", $i)) {
// Get the day of the week for the current day
$dayOfWeek = date("l", $i);
// If the day is Sunday, increment the counter
if ($dayOfWeek == "Sunday") {
$numSundays++;
}
}
// Print the number of Sundays
echo "Number of Sundays: $numSundays\n";
?>

How to exclude weekends between two dates using Moment.js

I am trying to exclude weekends in my JavaScript code. I use moment.js and having difficulty choosing the right variable for 'days'.
So far I have thought that I need to exclude day 6 (saturday) and day 0 (sunday) by changing the weekday variable to count from day 1 to day 5 only. But not sure how it changes.
My jsfiddle is shown here: FIDDLE
HTML:
<div id="myContent">
<input type="radio" value="types" class="syncTypes" name="syncTypes"> <td><label for="xshipping.xshipping1">Free Shipping: (<span id="fsv1" value="5">5</span> to <span id="fsv2" value="10">10</span> working days)</label> </td><br>
<div id="contacts" style="display:none;border:1px #666 solid;padding:3px;top:15px;position:relative;margin-bottom:25px;">
Contacts
</div>
<input type="radio" value="groups" class="syncTypes" name="syncTypes"> <td><label for="xshipping.xshipping2">Express Shipping: (<span id="esv1" value="3">3</span> to <span id="esv2" value="4">4</span> working days)</label> </td>
<div id="groups" style="display:none;border:1px #666 solid;padding:3px;top:15px;position:relative">
Groups
</div>
</div>
JavaScript:
var a = 5; //Free shipping between a
var b = 10;//and b
var c = 3;//Express shipping between c
var d = 4;//and d
var now = moment();
var f = "Your item will be delivered between " + now.add("days",a).format("Do MMMM") + " and " + now.add("days",b).format("Do MMMM");
var g = "Your item will be delivered between " + now.add("days".c).format("Do MMMM") + " and " + now.add("days",d).format("Do MMMM");
var h = document.getElementById('contacts');
h.innerHTML = g
var i = document.getElementById('groups');
i.innerHTML = f
$(function() {
$types = $('.syncTypes');
$contacts = $('#contacts');
$groups = $('#groups');
$types.change(function() {
$this = $(this).val();
if ($this == "types") {
$groups.slideUp(300);
$contacts.delay(200).slideDown(300);
}
else if ($this == "groups") {
$contacts.slideUp(300);
$groups.delay(200).slideDown(300);
}
});
});

Here you go!
function addWeekdays(date, days) {
date = moment(date); // use a clone
while (days > 0) {
date = date.add(1, 'days');
// decrease "days" only if it's a weekday.
if (date.isoWeekday() !== 6 && date.isoWeekday() !== 7) {
days -= 1;
}
}
return date;
}
You call it like this
var date = addWeekdays(moment(), 5);
I used .isoWeekday instead of .weekday because it doesn't depend on the locale (.weekday(0) can be either Monday or Sunday).
Don't subtract weekdays, i.e addWeekdays(moment(), -3) otherwise this simple function will loop forever!
Updated JSFiddle http://jsfiddle.net/Xt2e6/39/ (using different momentjs cdn)

Those iteration looped solutions would not fit my needs.
They were too slow for large numbers.
So I made my own version:
https://github.com/leonardosantos/momentjs-business
Hope you find it useful.

https://github.com/andruhon/moment-weekday-calc plugin for momentJS might be helpful for similar tasks
It does not solves the exact problem, but it is able to calculate specific weekdays in the range.
Usage:
moment().isoWeekdayCalc({
rangeStart: '1 Apr 2015',
rangeEnd: '31 Mar 2016',
weekdays: [1,2,3,4,5], //weekdays Mon to Fri
exclusions: ['6 Apr 2015','7 Apr 2015'] //public holidays
}) //returns 260 (260 workdays excluding two public holidays)

If you want a pure JavaScript version (not relying on Moment.js) try this...
function addWeekdays(date, days) {
date.setDate(date.getDate());
var counter = 0;
if(days > 0 ){
while (counter < days) {
date.setDate(date.getDate() + 1 ); // Add a day to get the date tomorrow
var check = date.getDay(); // turns the date into a number (0 to 6)
if (check == 0 || check == 6) {
// Do nothing it's the weekend (0=Sun & 6=Sat)
}
else{
counter++; // It's a weekday so increase the counter
}
}
}
return date;
}
You call it like this...
var date = addWeekdays(new Date(), 3);
This function checks each next day to see if it falls on a Saturday (day 6) or Sunday (day 0). If true, the counter is not increased yet the date is increased.
This script is fine for small date increments like a month or less.

I would suggest adding a function to the moment prototype.
Something like this maybe? (untested)
nextWeekday : function () {
var day = this.clone(this);
day = day.add('days', 1);
while(day.weekday() == 0 || day.weekday() == 6){
day = day.add("days", 1);
}
return day;
},
nthWeekday : function (n) {
var day = this.clone(this);
for (var i=0;i<n;i++) {
day = day.nextWeekday();
}
return day;
},
And when you're done and written some tests, send in a pull request for bonus points.

d1 and d2 are moment dates passed as an argument to calculateBusinessDays
calculateBusinessDays(d1, d2) {
const days = d2.diff(d1, "days") + 1;
let newDay: any = d1.toDate(),
workingDays: number = 0,
sundays: number = 0,
saturdays: number = 0;
for (let i = 0; i < days; i++) {
const day = newDay.getDay();
newDay = d1.add(1, "days").toDate();
const isWeekend = ((day % 6) === 0);
if (!isWeekend) {
workingDays++;
}
else {
if (day === 6) saturdays++;
if (day === 0) sundays++;
}
}
console.log("Total Days:", days, "workingDays", workingDays, "saturdays", saturdays, "sundays", sundays);
return workingDays;
}

If you want a version of #acorio's code sample which is performant (using #Isantos's optimisation) and can deal with negative numbers use this:
moment.fn.addWorkdays = function (days) {
// Getting negative / positive increment
var increment = days / Math.abs(days);
// Looping weeks for each full 5 workdays
var date = this.clone().add(Math.floor(Math.abs(days) / 5) * 7 * increment, 'days');
// Account for starting on Saturdays and Sundays
if(date.isoWeekday() === 6) { date.add(-increment, 'days'); }
else if(date.isoWeekday() === 7) { date.add(-2 * increment, 'days'); }
// Adding / removing remaining days in a short loop, jumping over weekends
var remaining = days % 5;
while(remaining != 0) {
date.add(increment, 'days');
if(date.isoWeekday() !== 6 && date.isoWeekday() !== 7)
remaining -= increment;
}
return date;
};
See Fiddle here: http://jsfiddle.net/dain/5xrr79h0/
Edit: now fixed issue adding 5 days to a day initially on a weekend

I know this question was posted long ago, but in case somebody bump on this, here is optimized solution using moment.js:
function getBusinessDays(startDate, endDate){
var startDateMoment = moment(startDate);
var endDateMoment = moment(endDate)
var days = Math.round(startDateMoment.diff(endDateMoment, 'days') - startDateMoment .diff(endDateMoment, 'days') / 7 * 2);
if (endDateMoment.day() === 6) {
days--;
}
if (startDateMoment.day() === 7) {
days--;
}
return days;
}

const calcBusinessDays = (d1, d2) => {
// Calc all days used including last day ( the +1 )
const days = d2.diff(d1, 'days') + 1;
console.log('Days:', days);
// how many full weekends occured in this time span
const weekends = Math.floor( days / 7 );
console.log('Full Weekends:', weekends);
// Subtract all the weekend days
let businessDays = days - ( weekends * 2);
// Special case for weeks less than 7
if( weekends === 0 ){
const cur = d1.clone();
for( let i =0; i < days; i++ ){
if( cur.day() === 0 || cur.day() === 6 ){
businessDays--;
}
cur.add(1, 'days')
}
} else {
// If the last day is a saturday we need to account for it
if (d2.day() === 6 ) {
console.log('Extra weekend day (Saturday)');
businessDays--;
}
// If the first day is a sunday we need to account for it
if (d1.day() === 0) {
console.log('Extra weekend day (Sunday)');
businessDays--;
}
}
console.log('Business days:', businessDays);
return businessDays;
}

This can be done without looping between all dates in between.
// get nb of weekend days
var startDateMonday = startDate.clone().startOf('isoWeek');
var endDateMonday = endDate.clone().startOf('isoWeek');
var nbWeekEndDays = 2 * endDateMonday.diff(startDateMonday, 'days') / 7;
var isoDayStart = startDate.isoWeekday();
if (isoDayStart > 5) // starts during the weekend
{
nbWeekEndDays -= (8 - isoDayStart);
}
var isoDayEnd = endDate.isoWeekday();
if (isoDayEnd > 5) // ends during the weekend
{
nbWeekEndDays += (8 - isoDayEnd);
}
// if we want to also exlcude holidays
var startOfStartDate = startDate.clone().startOf('day');
var nbHolidays = holidays.filter(h => {
return h.isSameOrAfter(startOfStartDate) && h.isSameOrBefore(endDate);
}).length;
var duration = moment.duration(endDate.diff(startDate));
duration = duration.subtract({ days: nbWeekEndDays + nbHolidays });
var nbWorkingDays = Math.floor(duration.asDays()); // get only nb of complete days

I am iterating from start date to end date and only counting days which are weekdays.
const calculateBusinessDays = (start_date, end_date) => {
const d1 = start_date.clone();
let num_days = 0;
while(end_date.diff(d1.add(1, 'days')) > 0) {
if ([0, 6].includes(d1.day())) {
// Don't count the days
} else {
num_days++;
}
}
return num_days;
}