How to do calendar operations in Java GWT? How to add days to a Date?

Updated answer for GWT 2.1

final Date dueDate = new Date();CalendarUtil.addDaysToDate(dueDate, 21);

Edit: the fully qualified name of this class is com.google.gwt.user.datepicker.client.CalendarUtil.

The answer that Google seems to use (currently), is:

  @SuppressWarnings("deprecation") // GWT requires Date  public static void addDaysToDate(Date date, int days) {    date.setDate(date.getDate() + days);  }

This is from the class com.google.gwt.user.datepicker.client.CalendarUtil, which is used by com.google.gwt.user.datepicker.client.DatePicker. I imagine, that there will be problems involved, when doing calculations in different timezones.

Lots of people have already voted for some kind of Joda time for GWT: http://code.google.com/p/google-web-toolkit/issues/detail?id=603 . The currently last comment states, that there's a new fork of goda time, maybe we should really check it out.

private static final long MILLISECONDS_IN_SECOND = 1000l;private static final long SECONDS_IN_MINUTE = 60l;private static final long MINUTES_IN_HOUR = 60l;private static final long HOURS_IN_DAY = 24l;private static final long MILLISECONDS_IN_DAY = MILLISECONDS_IN_SECOND *        SECONDS_IN_MINUTE *        MINUTES_IN_HOUR *        HOURS_IN_DAY;public Date addDays (Date date, days){ return new Date (date.getTime () + (days * MILLISECONDS_IN_DAY));}

this will work with leap years but will eventually stray by milliseconds on milleniums when we add or drop leap seconds.