Calendar Week Number: 2025-39

Current week of year! Always looking up the current calendar week number? No Problem. Here it is! Find the calendar week numbers for the next years. Check dates, timestamps and daylight saving time of weeks.

Examples: today, -14182940, 2020-01-01, 2020-01-01 20:11:21, next monday, 2000-W09 1970-01
Current Week

Calendar Week 39 in 2025

Mon. 2025-09-22 — Sun. 2025-09-28

Week 39 of Year 2025

Week Number39
StartsMon. 2025-09-22
EndsSun. 2025-09-28
Your TimezoneAmerica/New_York
Timezone OffsetEDT (-04:00)
Daylight SavingYes (2025-09-28)
TimestampsFrom 1758513600 to 1759118399
ISO 8601 Week2025W39
ISO 8601 Year / Week2025 / 39
Set DateSun. 2025-09-28
Previous Week Next Week
All weeks of 2025: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

Activate Calendar Weeks in Outlook 365

To show the week number in your Outlook calendar, you have to activate this in your calendar settings. Go to Settings => Calendar => View (HERE) and activate the option: "Show week numbers". Outlook 365 week numbers setting

Getting Week numbers in Excel 365

You can calculate the week number in Excel 365 from a date with the ISOWEEKNUM() function. There is also a second function for week numbers. WEEKNUM() starts counting in the week of January 1st. The ISO weeks starts with 1 in the week with the first Thursday of the year.

The functions WEEKNUM() and ISOWEEKNUM() are also available in Google Spreadsheets. Excel 365 week numbers

About Week Numbers

Weeks in a Gregorian calendar year can be numbered for each year. This style of numbering is often used in European and Asian countries. It is less common in the U.S. and elsewhere.

The system for numbering weeks is the ISO week date system, which is included in ISO 8601. This system dictates that each week begins on a Monday and is associated with the year that contains that week's Thursday.

More on Wikipedia: Week Numbering

First week of year - Week W01

The first week is the week with the starting year's first Thursday in it (the formal ISO definition). There are some other definitions with the same result: The week with 4 January in it, the first week with the majority (four or more) of its days in the starting year or the week starting with the Monday in the period 29 December - 4 January.

Week 1 (W01) of 2025 goes from 2024-12-30 to 2025-01-05.

More on Wikipedia: ISO 8601

Last week of year - Week W52

28. December is always in the last week of its year. The week number can be described by counting the Thursdays: week 12 contains the 12th Thursday of the year.

Week 52 (W52) of 2025 goes from 2025-12-28 to 2026-01-03.

More on Wikipedia: ISO 8601

Current Week Numbers in Different Programming Languages

Current Week number in PHP 
$week = date('W');
Week number from Date in PHP 
$localDate = new \DateTime();
$localDate->setISODate(2025, 39);
$localDate->setTime(0, 0);
Javascript Current Week 
Date.prototype.getWeek = function () {

    var target = new Date(this.valueOf());
    var dayNr = (this.getDay() + 6) % 7;

    target.setDate(target.getDate() - dayNr + 3);

    var firstThursday = target.valueOf();
    target.setMonth(0, 1);

    if (target.getDay() !== 4) {
        target.setMonth(0, 1 + ((4 - target.getDay()) + 7) % 7);
    }

    return 1 + Math.ceil((firstThursday - target) / 604800000);
}

var aDate = new Date('2025-09-01');
alert(aDate.getWeek()); // Result: 39
Current Week in Python 
from datetime import date
weekNumber = date.today().isocalendar()[1]
Calendar Week in Java 
Calendar calendar = new GregorianCalendar();
calendar.set(2025, 9, 1);
int weekOfYear = calendar.get(Calendar.WEEK_OF_YEAR); // Result: 39
Current Week with MySQL 
SELECT WEEKOFYEAR(NOW());
SELECT WEEKOFYEAR('2021-01-02');
Current Week with GO 
import "fmt"
import "time"

var timeNow := time.Now()
var _, wkNum := timeNow.ISOWeek()
Current Week with C 
#include <stdio.h>
#include <time.h>

int main()
{
    time_t rawtime;
    struct tm * timeinfo;
    char buffer [80];

    time (&rawtime);
    timeinfo = localtime (&rawtime);

    strftime (buffer,80,"Week: %U",timeinfo);
    puts (buffer);

    return 0;
}
Current Week with C# 
using System;
using System.Globalization;

public class SamplesCalendar  {
   public static void Main()  {
      CultureInfo myCI = new CultureInfo("en-US");
      Calendar myCal = myCI.Calendar;

      CalendarWeekRule myCWR = myCI.DateTimeFormat.CalendarWeekRule;
      DayOfWeek myFirstDOW = myCI.DateTimeFormat.FirstDayOfWeek;

      Console.WriteLine( "Week: {0}", myCal.GetWeekOfYear( DateTime.Now, myCWR, myFirstDOW ));
   }
}