static java.util.Calendar calendarFromYMD(int year, int month, int day) {
  java.util.Calendar c = java.util.Calendar.getInstance();
  c.set(java.util.Calendar.YEAR, year);
  c.set(java.util.Calendar.MONTH, month-1);
  c.set(java.util.Calendar.DATE, day);
  ret c;
}