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Customizing js-joda

This package is extensible, allowing you to create your own custom temporal calculations. See the temporal interface documentation for more information.

Custom temporal adjuster

// implement a TemporalAdjuster that the next or same even day of month
var nextOrSameEvenDay = {
  adjustInto: function(t) {
    return t.dayOfMonth() % 2 === 0 ? t : t.plusDays(1);

LocalDateTime.parse("2012-12-23T12:00").with(nextOrSameEvenDay); // '2012-12-24T12:00'
LocalDate.parse("2012-12-24").with(nextOrSameEvenDay); // '2012-12-24'

Custom temporal fields and temporal units

See the source for temporal/IsoFields as an example how to implement custom fields and units. IsoFields implements fields and units for an ISO week-based year.

Custom formatter and queries

The following example implements a parser for a local date with an optional local time. It returns either a LocalDate or a LocalDateTime, depending on the parsed fields.

// build a custom date time formatter where the time field is optional
var OPTIONAL_FORMATTER = DateTimeFormatter.ofPattern(

// create a temporal query that create a new Temporal depending on the existing fields
dateOrDateTimeQuery = {
  queryFrom: function(temporal) {
    var date = temporal.query(TemporalQueries.localDate());
    var time = temporal.query(TemporalQueries.localTime());
    if (time == null) return date;
    else return date.atTime(time);

localDate = OPTIONAL_FORMATTER.parse('2012-12-24', dateOrDateTimeQuery);
localDateTime = OPTIONAL_FORMATTER.parse(