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  *  Copyright 2001-2013 Stephen Colebourne
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
package org.joda.time;
Exception thrown when attempting to create an instant or date-time that cannot exist.

Classes like DateTime only store valid date-times. One of the cases where validity is important is handling daylight savings time (DST). In many places DST is used, where the local clock moves forward by an hour in spring and back by an hour in autumn/fall. This means that in spring, there is a "gap" where a local time does not exist.

This exception refers to this gap, and it means that your application tried to create a date-time inside the gap - a time that did not exist. Since Joda-Time objects must be valid, this is not allowed.

Possible solutions may be as follows:
Use LocalDateTime, as all local date-times are valid.
When converting a LocalDate to a DateTime, then use toDateTimeAsStartOfDay() as this handles and manages any gaps.
When parsing, use parseLocalDateTime() if the string being parsed has no time-zone.

Stephen Colebourne
public class IllegalInstantException extends IllegalArgumentException {
Serialization lock.
    private static final long serialVersionUID = 2858712538216L;


message the message
    public IllegalInstantException(String message) {


instantLocal the local instant
zoneId the time-zone ID, may be null
    public IllegalInstantException(long instantLocalString zoneId) {
    private static String createMessage(long instantLocalString zoneId) {
        String localDateTime = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS").print(new Instant(instantLocal));
        String zone = (zoneId != null ? " (" + zoneId + ")" : "");
        return "Illegal instant due to time zone offset transition (daylight savings time 'gap'): " + localDateTime + zone;
Checks if the exception is, or has a cause, of IllegalInstantException.

ex the exception to check
true if an IllegalInstantException
    public static boolean isIllegalInstant(Throwable ex) {
        if (ex instanceof IllegalInstantException) {
            return true;
        while (ex.getCause() != null && ex.getCause() != ex) {
            return isIllegalInstant(ex.getCause());
        return false;
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