Which timezone is java.sql.Date toLocalDate using

Question

I'm surprised that java.sql.Date has a method toLocalDate().

java.util.Date or java.time.Instant don't have comparable methods. It seems that in java.time, a ZoneId must always be provided to obtain "LocalFoo" or "OffsetBar".

From the javadoc of java.sql.Date#toLocalDate():

Converts this Date object to a LocalDate. The conversion creates a LocalDate that represents the same date value as this Date in local time zone

Which timezone is "local time zone"? Does it depend on database or JVM settings?

It depends on JVM settings, for example on system property "user.timezone", too, see also getting default zone — Meno Hochschild
– Meno Hochschild, Commented Jun 9, 2016 at 12:00
Are you sure? It seems a bit odd with the other parts of java.time, that this default can not be overridden or made explicit. — Lars Bohl
– Lars Bohl, Commented Jun 9, 2016 at 12:02
Possible duplicate of Timezones in SQL DATE vs java.sql.Date — Jordi Castilla
– Jordi Castilla, Commented Jun 9, 2016 at 12:05
That question looks very related, and I guess it means that it depends on system settings indeed. However toLocalDate is not mentioned there, and an explicit answer to that specific question would be nice. — Lars Bohl
– Lars Bohl, Commented Jun 9, 2016 at 12:19

Basil Bourque · Accepted Answer · 2016-06-09 21:10:37Z

5

Conceptually, a java.sql.Date is the same as a LocalDate, ie. a date without time or time-zone. In practice, because java.sql.Date is implemented based on a long milliseconds, it has an implicit use of the system time-zone. So, the toLocalDate() method exists because the Java SQL spec leads want you to think of java.sql.Date as being without a time-zone.

edited Jun 9, 2016 at 21:10

Basil Bourque

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answered Jun 9, 2016 at 12:05

JodaStephen

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2 Comments

Lars Bohl Over a year ago

Does that mean that date.toLocalDate() will return different LocalDate objects, depending on the system timezone of the current JVM?

marcus Over a year ago

So that's why the method has @SuppressWarnings("deprecation")? It's funny because java.util.Date deprecates most methods and java.sql.Date undeprecates some of them...

MarkusAchenbach · Accepted Answer · 2016-06-09 19:25:12Z

2

given a java.sql.Date-Object wrapping a fix millisecondsvalue, you will indeed get different LocalDate-Values depending on the Default-Timezone on your System.

I tried the following Code-Snippet:

TimeZone.setDefault(TimeZone.getTimeZone("America/Los_Angeles"));
java.sql.Date sqlDate = new java.sql.Date(1465485798671l);
System.out.println(sqlDate.toLocalDate());
TimeZone.setDefault(TimeZone.getTimeZone("Asia/Tokyo"));
System.out.println(sqlDate.toLocalDate());

which yields: 2016-06-09 2016-06-10

edited Jun 9, 2016 at 19:25

answered Jun 9, 2016 at 15:31

MarkusAchenbach

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3 Comments

Lars Bohl Over a year ago

Hang on, there's no toLocalDate in that code. What happens when we add it?

MarkusAchenbach Over a year ago

Hi Lars, sorry I forgot indeed to add .toLocalDate() - i've edited the code.

Lars Bohl Over a year ago

Excellent answer. Accepted!

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