How to convert Joda Localdate to Joda DateTime?

Question

I'm trying to simply add TimeZone information back into a LocalDate before performing some more calculations. The LocalDate came from using the ObjectLab LocalDateCalculator to add days to an existing DateTime but the method needs to return a modified ReadableInstant to form an Interval which I can then inspect.

The code I'm trying amounts to a conversion of Joda LocalDate to Joda DateTime:

LocalDate contextLocalBusinessDate = calculator.getCurrentBusinessDate(); DateTime businessDateAsInContextLocation = new DateTime(contextLocalBusinessDate, contextTimeZone); 

The error I get is from Joda's conversion system:

java.lang.IllegalArgumentException: No instant converter found for type: org.joda.time.LocalDate         at org.joda.time.convert.ConverterManager.getInstantConverter(ConverterManager.java:165)         at org.joda.time.base.BaseDateTime.<init>(BaseDateTime.java:147)         at org.joda.time.DateTime.<init>(DateTime.java:192) 

I'm looking for a fix to this problem, or a workaround that results in an accurate Interval with full timezone information.

Answer 1

There are various methods on LocalDate for this, including:

• LocalDate::toDateTimeAtCurrentTime()
• LocalDate::toDateTimeAtStartOfDay()
• LocalDate::toDateTime( LocalTime )
• LocalDate::toDateTime( LocalTime , DateTimeZone )

You have to be explicit about what you want the time component to be in the resulting DateTime object, which is why DateTime's general-conversion constructor can't do it.

Answer 2

java.time

Quoted below is a notice from the home page of Joda-Time:

Note that from Java SE 8 onwards, users are asked to migrate to java.time (JSR-310) - a core part of the JDK which replaces this project.

Solution using java.time, the modern Date-Time API:

A common way to convert a LocalDate to ZonedDateTime is to first convert it to LocalDateTime with 00:00 hours using LocalDate#atStartOfDay and then combine with a ZoneId. An alternative to LocalDate#atStartOfDay is LocalDate#atTime(LocalTime.MIN).

Note that LocalDate#atStartOfDay(ZoneId) is another variant of atStartOfDay. However, it may not return a ZonedDateTime with 00:00 hours on the day of DST transition.

You can convert from ZonedDateTime to OffsetDateTime using ZonedDateTime#toOffsetDateTime.

Demo:

import java.time.LocalDate; import java.time.OffsetDateTime; import java.time.ZoneId; import java.time.ZonedDateTime;  public class Main {     public static void main(String[] args) {         LocalDate today = LocalDate.now();         // Note: Change the ZoneId as applicable e.g. ZoneId.of("Europe/London")          ZonedDateTime zdt = today.atStartOfDay().atZone(ZoneId.systemDefault());         System.out.println(zdt);          OffsetDateTime odt = zdt.toOffsetDateTime();         System.out.println(odt);     } } 

Output:

2021-07-11T00:00+01:00[Europe/London] 2021-07-11T00:00+01:00 

ONLINE DEMO

Learn more about the modern Date-Time API from Trail: Date Time.

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^{* For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7. If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring and How to use ThreeTenABP in Android Project.}