calculate week number of year

[Manolo Garcia Carrasco]

Hello, I need to calculate the number of weeks in a year from a date entered in a field.

[try67]

Google: "javascript get week number from date"

[bebarth]

Here is the adaptation to the US date format of a file shared on the French forum a few years ago.
The next year with 53 weeks will be in 2026 (the previous one was in 2020).
@+

[Manolo Garcia Carrasco]

What I really need is that from a date field (DATE) I get the result in another field (WEEK).

[try67]

Find a function that does that and we'll help you integrate it into the form.

[Manolo Garcia Carrasco]

// This script is released to the public domain and may be used, modified and
// distributed without restrictions. Attribution not necessary but appreciated.
// Source: https://weeknumber.com/how-to/javascript

// Returns the ISO week of the date.
Date.prototype.getWeek = function() {
var date = new Date(this.getTime());
date.setHours(0, 0, 0, 0);
// Thursday in current week decides the year.
date.setDate(date.getDate() + 3 - (date.getDay() + 6) % 7);
// January 4 is always in week 1.
var week1 = new Date(date.getFullYear(), 0, 4);
// Adjust to Thursday in week 1 and count number of weeks from date to week1.
return 1 + Math.round(((date.getTime() - week1.getTime()) / 86400000
- 3 + (week1.getDay() + 6) % 7) / 7);
}

// Returns the four-digit year corresponding to the ISO week of the date.
Date.prototype.getWeekYear = function() {
var date = new Date(this.getTime());
date.setDate(date.getDate() + 3 - (date.getDay() + 6) % 7);
return date.getFullYear();
}

[Manolo Garcia Carrasco]

What I really need is that from a date field (MYDATE) get the week number of the year where the result appears another field (WEEK).
For example:
MYDATE (yymmdd): 210803
WEEK: 31

[bebarth]

As you only indicate one date field, I guess the calculation must be done with the actual date.

Here is a validation script:

if (event.value!="") {
	var theDay=new Date(util.printd("mm/dd/yyyy", new Date(event.value))); 
	var timeDifference=new Date().getTime()-theDay.getTime();
	if (timeDifference>=0) {
		this.getField("theWeeks").value=Math.round(timeDifference/1000/3600/24/7);
	} else {
		app.alert("The indicated date must be earlier than today ",3);
		event.rc=false;
	}
} else {
	this.getField("theWeeks").value="";
}

[Manolo Garcia Carrasco]

What I really need is that from a date field (MYDATE) get the week number of the year where the result appears another field (WEEK).
For example:
MYDATE (yymmdd): 210803
WEEK: 31

[try67 · Accepted solution]

You can use this code, based on the function you provided above, as the custom Calculation script of the WEEK field:

var s = this.getField("MYDATE").valueAsString;
if (s=="") event.value = "";
else {
	var d = util.scand("yymmdd", s);
	event.value = getWeekNumber(d);
}

function getWeekNumber(date) {
	date.setHours(0, 0, 0, 0);
	// Thursday in current week decides the year.
	date.setDate(date.getDate() + 3 - (date.getDay() + 6) % 7);
	// January 4 is always in week 1.
	var week1 = new Date(date.getFullYear(), 0, 4);
	// Adjust to Thursday in week 1 and count number of weeks from date to week1.
	return 1 + Math.round(((date.getTime() - week1.getTime()) / 86400000
		- 3 + (week1.getDay() + 6) % 7) / 7);
}

[Manolo Garcia Carrasco]

Thank you very much for your time

[Manolo Garcia Carrasco]

It works very well but I need the result to be in double digits.
For example:
If I type 210916 the result is 37, but if I type 220103 the result is 1, this result is correct but I am interested that it is 01.

JANUARY > 01
FEBRUARY > 02
MARCH > 03
APRIL > 04
MAY > 05...

[try67 · Accepted solution]

After this line:

event.value = getWeekNumber(d);

Add this:

if (event.value.length==1) event.value = "0"+event.value;

[Manolo Garcia Carrasco]

Perfect, thank you very much for your professionalism.