Add weeks to date

Opposite of subtracting weeks from a java date, this example will show how to add weeks to a date using Calendar.add, java 8 date time api, joda DateTime.plusWeeks and apache common DateUtils.addWeeks. In the examples below, we will set a date that represents christmas, December 25th, then add a week to return a date representing new years day or January 1st.

Straight up Java

@Test
public void add_weeks_to_date_in_java () {
    
    Calendar xmas = Calendar.getInstance();
    xmas.set(2012, 11, 25, 0, 0, 0);
    
    Calendar newYearsDay = Calendar.getInstance();
    newYearsDay.setTimeInMillis(xmas.getTimeInMillis());
    newYearsDay.add(Calendar.WEEK_OF_YEAR, 1);     
    
    SimpleDateFormat dateFormatter = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss z");

    logger.info(dateFormatter.format(xmas.getTime()));
    logger.info(dateFormatter.format(newYearsDay.getTime()));

    assertTrue(newYearsDay.after(xmas));
}

Output

12/25/2012 00:00:00 CST
01/01/2013 00:00:00 CST

Java 8 Date and Time API

Java 8 LocalDateTime.plusWeeks will return a copy of the LocalDateTime with the specified number of weeks added.

@Test
public void add_weeks_to_date_in_java8() {

    LocalDateTime xmas = LocalDateTime.of(2012, Month.DECEMBER, 25, 0, 0);
    LocalDateTime newYearsDay = xmas.plusWeeks(1);

    java.time.format.DateTimeFormatter formatter = java.time.format.DateTimeFormatter
            .ofPattern("MM/dd/yyyy HH:mm:ss S");

    logger.info(xmas.format(formatter));
    logger.info(newYearsDay.format(formatter));

    assertTrue(newYearsDay.isAfter(xmas));
}

Output

12/25/2012 00:00:00 0
01/01/2013 00:00:00 0

Joda Time

Joda DateTime.plusWeeks will return a copy the DateTime plus the specified number of weeks.

@Test
public void add_weeks_to_date_in_java_with_joda () {

    DateTime xmas = new DateTime(2012, 12, 25, 0, 0, 0, 0);
    DateTime newYearsDay = xmas.plusWeeks(1);

    DateTimeFormatter fmt = DateTimeFormat.forPattern("MM/dd/yyyy HH:mm:ss z");
    
    logger.info(xmas.toString(fmt));
    logger.info(newYearsDay.toString(fmt));

    assertTrue(newYearsDay.isAfter(xmas));
}

Output

12/25/2012 00:00:00 CST
01/01/2013 00:00:00 CST

Apache Commons

Apache commons DateUtils.addWeeks will adds a number of weeks to the date returning a new object.

@Test
public void add_weeks_to_date_in_java_with_apachecommons () {

    Calendar xmas = Calendar.getInstance();
    xmas.set(2012, 11, 25, 0, 0, 0);
    
    Date newYearsDay = DateUtils.addWeeks(xmas.getTime(), 1);
    
    SimpleDateFormat dateFormatter = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss z");

    logger.info(dateFormatter.format(xmas.getTime()));
    logger.info(dateFormatter.format(newYearsDay));

    assertTrue(newYearsDay.after(xmas.getTime()));
}

Output

12/25/2012 00:00:00 CST
01/01/2013 00:00:00 CST