Get third friday of a month

Question

I am developing a local calendar for my application. but the is an issue with monthly repeat event (day of week).

When i am create an event starting on 16-9-2016(16 SEP 2016 FRIDAY) and repeating Third Friday of each month. but next month it create on second Friday 14-10-2016 (This is the issue). next month it will be on third Friday.

my code is

public Date nthWeekdayOfMonth(int dayOfWeek, int month, int year, int week, TimeZone timeZone) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTimeZone(timeZone);
        calendar.set(Calendar.DAY_OF_WEEK, dayOfWeek);
        calendar.set(Calendar.WEEK_OF_MONTH, week);
        calendar.set(Calendar.MONTH, month);
        calendar.set(Calendar.YEAR, year);
        return calendar.getTime();
    }

I know the issue. but i don`t know how to fix it.. is there any way to fix it ?

Answer 1

You code seems to be working completely fine, there is nothing that is going wrong from what I can see, it may be that your parameters are wrong.

It is important to note that MONTH and DAY are 0-based so, 0 = January and 0 = Sunday so your parameters for getting the third friday should look like the following:

nthWeekdayOfMonth(6, 9, 2016, 3, TimeZone.getTimeZone("Europe/London"));

Which returns the following output:

Fri Oct 21 11:06:33 BST 2016

To break it down:

1. Day of week is 6, because Sunday = 0.
2. Month is 9 - i.e. October
3. Year is normal - 2016
4. Week is NOT 0-based so 3rd week will be index 3
5. TimeZone as normal

Please see the Calendar documentation for reference.

---

EDIT

So for some reason, it works on my machine but it doesn't on others; I don't know what the issue could be with that but using DAY_OF_WEEK_IN_MONTH seems to be a better option for this:

public static Date nthWeekdayOfMonth(int dayOfWeek, int month, int year, int week, TimeZone timeZone) {
    Calendar calendar = Calendar.getInstance();
    calendar.setTimeZone(timeZone);
    calendar.set(Calendar.DAY_OF_WEEK, dayOfWeek);
    //calendar.set(Calendar.WEEK_OF_MONTH, week);
    calendar.set(Calendar.DAY_OF_WEEK_IN_MONTH, week);
    calendar.set(Calendar.MONTH, month);
    calendar.set(Calendar.YEAR, year);
    return calendar.getTime();
}

I usually use GregorianCalendar but Calendar should work just fine.

This should (hopefully) work for the most part, I've tested it on other machines and ideone.

Answer 2

I could propose next decision:

public Date nthWeekdayOfMonth(int dayOfWeek, int month, int year, int week, TimeZone timeZone) {
    Calendar calendar = Calendar.getInstance();
    calendar.setTimeZone(timeZone);
    calendar.set(Calendar.YEAR, year);
    calendar.set(Calendar.MONTH, month);
    calendar.set(Calendar.DAY_OF_MONTH, 1);
    // add +1 to week if first weekday of mounth > dayOfWeek
    int localWeek = week;
    if (calendar.get(calendar.DAY_OF_WEEK) > dayOfWeek) {
        localWeek++;
    }
    calendar.set(Calendar.WEEK_OF_MONTH, localWeek);
    calendar.set(Calendar.DAY_OF_WEEK, dayOfWeek);
    return calendar.getTime();
}

for:

System.out.println(nthWeekdayOfMonth(Calendar.FRIDAY, Calendar.SEPTEMBER, 2016, 3, TimeZone.getTimeZone("Europe/London")));
System.out.println(nthWeekdayOfMonth(Calendar.FRIDAY, Calendar.OCTOBER, 2016, 3, TimeZone.getTimeZone("Europe/London")));
System.out.println(nthWeekdayOfMonth(Calendar.FRIDAY, Calendar.NOVEMBER, 2016, 3, TimeZone.getTimeZone("Europe/London")));

it returns:

Fri Sep 16 19:41:23 YEKT 2016
Fri Oct 21 19:41:23 YEKT 2016
Fri Nov 18 20:41:23 YEKT 2016