Adding a number of days to a JodaTime Instant

datetime, java, jodatime

Solution

This is the solution that was chosen.

/**
* Zone to use for input and output
*/
private static final DateTimeZone ZONE = DateTimeZone.forId("Europe/London");

/**
 * Adds a number of days specified to the instant in time specified.
 *
 * @param instant - the date to be added to
 * @param numberOfDaysToAdd - the number of days to be added to the instant specified
 * @return an instant that has been incremented by the number of days specified
 */
public static Instant addNumberOfDaysToInstant(final Instant instant, final int numberOfDaysToAdd) {
    return instant.toDateTime(ZONE).withFieldAdded(DurationFieldType.days(), numberOfDaysToAdd).toInstant();
}

Problem

I'm trying to write a simple utility method for adding aninteger number of days to a Joda time instant. Here is my first stab. ``` /** * Adds a number of days specified to the instant in time specified. * * @param instant - the date to be added to * @param numberOfDaysToAdd - the number of days to be added to the instant specified * @return an instant that has been incremented by the number of days specified */ public static Instant addNumberOfDaysToInstant(final Instant instant, final int numberOfDaysToAdd) { Days days = Days.days(numberOfDaysToAdd); Interval interval = new Interval(instant, days); return interval.getEnd().toInstant(); } ``` This works fine for the most part except when you consider the example when the number of days added takes you across the BST / GMT boundary. Here is a small example. ``` public class DateAddTest { ``` /** * Zone to use for input and output */ private static final DateTimeZone ZONE = DateTimeZone.forId("Europe/London"); ``` /** * Formatter used to translate Instant objects to & from strings. */ private static final DateTimeFormatter FORMATTER = DateTimeFormat.forPattern(DATE_FORMAT).withZone(ZONE); /** * Date format to be used */ private static final String DATE_FORMAT = "dd/MM/yyyy"; public static void main(String[] args) { DateTime dateTime = FORMATTER.parseDateTime("24/10/2009"); Instant toAdd = dateTime.toInstant(); Instant answer = JodaTimeUtils.addNumberOfDaysToInstant(toAdd, 2); System.out.println(answer.toString(FORMATTER)); //25/10/2009 } ``` } I think this problem is because the interval does not take into acount the fact that it has crossing the bst boundary. Any ideas of a better way to implement this would be appreciated.

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