Javascript : Calculate business days between two (2) dates, business days (Monday to Friday)

JS: Calc business days Monday to Friday

function calculateBusinessDays(startDate, endDate){
// Validate input
if (endDate < startDate)
    return 0;

// Calculate days between dates
var millisecondsPerDay = 86400 * 1000; // Day in milliseconds
startDate.setHours(0,0,0,1);  // Start just after midnight
endDate.setHours(23,59,59,999);  // End just before midnight
var diff = endDate - startDate;  // Milliseconds between datetime objects    
var days = Math.ceil(diff / millisecondsPerDay);

// Subtract two weekend days for every week in between
var weeks = Math.floor(days / 7);
days = days - (weeks * 2);

// Handle special cases
var startDay = startDate.getDay();
var endDay = endDate.getDay();

// Remove weekend not previously removed.   
if (startDay - endDay > 1)         
    days = days - 2;      

// Remove start day if span starts on Sunday but ends before Saturday
if (startDay == 0 && endDay != 6) {
    days = days - 1;  
}

// Remove end day if span ends on Saturday but starts after Sunday
if (endDay == 6 && startDay != 0) {
    days = days - 1;
}

return days;
}

Great code, there is just one issue when dates are in different daylight saving times. See result with these dates (30. is where daylight saving time changes in our country):

const from = new Date("2022-10-30");
const to = new Date("2022-11-04");

5 Days would be expected result. But function returns 4. I managed to fix this issue by adding:

    const vTimezoneDiff = endDate.getTimezoneOffset() - startDate.getTimezoneOffset();
    if (vTimezoneDiff != 0) {
        // Handle daylight saving time difference between two dates.
        startDate.setMinutes(startDate.getMinutes() + vTimezoneDiff);
    }

Just after time normalization. Hope it helps you or others finding this function ;-)

@sadovsf Hi!, I also had problems in the differences, I solved it based on the date in UTC, change the functions for example from getDay to getUTCDay, because the day 2022-10-30 is Sunday, and getDay takes me as 6, it should be 0

Thank you, i would have to test it. Solution I provided is working as expected (I did autotests to validate that and using it in app iam building which relies on it heavily)

This would be great if you could have an option that deals with holidays as well...just saying...

there is one issue with this code if you enter following date
start date=april 10 2023
end date=april 17 2023
it returning 5 instead of 6
every monday is not counted if you can check