I’d like to have a function which returns the next week and year given

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Asked: June 11, 20262026-06-11T15:54:31+00:00 2026-06-11T15:54:31+00:00

I’d like to have a function which returns the next week and year given

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I’d like to have a function which returns the next week and year given a week and year. It looks something like:

public static int[] getNextWeek(int year, int week) {
    Calendar c = Calendar.getInstance(); // I'm Locale.US and TimeZone "America/New_York"
    c.clear();
    c.set(Calendar.YEAR, year);
    c.set(Calendar.WEEK_OF_YEAR, week);

    c.add(Calendar.WEEK_OF_YEAR, 1);

    return new int[] {c.get(Calendar.YEAR), c.get(Calendar.WEEK_OF_YEAR)}
}

This sometimes does not work around year boundaries. It seems to depend on what day you invoke it and for what parameters you use! For example, if I invoke it with year 2012 and week 52 then I expect the result to be year 2013 and week 1. If you invoke it today (Tuesday July 17 2012) it works. If you set the day of week to yesterday it does not; and oddly results in year 2012 week 1. Weird. What is going on? It appears to relate to the day of the week because it doesn’t work if invoked with SUNDAY or MONDAY, which are the last two days of 2012! If I set the day of the week to the last day of the week the function seems to work; before calling Calendar.add() I do:

    // Must set to last day of week; initially set to first day due to API
    c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek()); // SUNDAY
    c.add(Calendar.DAY_OF_WEEK, 6); // Must roll forward not backwards

There doesn’t seem to be any weirdness like this if I create a getPreviousWeek method. Is this a java.util.Calendar bug? Next time I guess I’ll use Joda time!