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Get current week number

  • Hi,

    I'm looking for a way to get the current week number. I had a look at the date object but couldn't find a method for it. Any idea how to get/calculate the week number?


  • Lifetime Qt Champion


    The QDate class has a method for that.

  • Hi,

    thanks for the answer. How can I use QDate from within a QML script? Soemthing like "new QDate()" seems not to work.

    And the date object returns a "undefined" if I try to access weekNumber:

    var d = new Date();


  • @schiessle hi
    that is c++ method

     QDate date(2019,03,07); 
     int weekNbr = date.weekNumber();

    you can do this and make weekNbr reachable from QML using setContextProperty() method:

    int main(int argc, char *argv[])
        QGuiApplication app(argc, argv);
        QQmlApplicationEngine engine;
         QDate date(2019,03,07);  
         int weekNbr = date.weekNumber();
    //use it in QML
    Component.onCompleted: {console.log("weekNbr : " + weekNbr)}

    or full js : (source

    Component.onCompleted: {
        var date = new 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.
        console.log(1 + Math.round(((date.getTime() - week1.getTime()) / 86400000
                                    - 3 + (week1.getDay() + 6) % 7) / 7))

  • @LeLev Thanks for the detailed example and the link to the JavaScript example.

    I chosed the JavaScript way and it works nicely!

    Background: I use a Qt program which allows to write "plugins" as QML scripts. I want to write such a plugin. Therefore I need a way to get the week number without patching the main program to expose the week number. That's why I choosed the JS way.

  • @LeLev Careful with those js libraries, if you want valid week numbers on the year 2029 or later, maybe choose another library. It just did a quick test (someone please verify)
    0_1552082185598_Screenshot from 2019-03-08 22-42-00.png
    0_1552082194231_Screenshot from 2019-03-08 22-52-32.png 0_1552082201824_Screenshot from 2019-03-08 22-53-19.png
    The first difference I found is on New Year's Eve 2029 (see first picture, screen shot of my Ubuntu 18.04)

    2nd picture is a dump of weeknumber using that javascript code, ranging from December 28 to January 4 the following year (i.e. 8 days in a row).

    3rd picture is a similar dump using QDate.weekNumber();
    (Also New Year's Eve 2035 differs)

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