[hibernate-dev] HHH-11396 - Timezone handling

[Christian Beikov]

Hey everyone,

I'd like to get your opinion on something. We had this issues regarding 
timezone handling which Vlad closed pretty quickly saying it isn't a 
Hibernate problem and I generally agree, but still would like to know 
what you think about it.

So basically what we do in the LocalDateJavaDescriptor(and also in some 
other places) is to use the value returned by java.sql.Date in some way 
and pack that into the target type. In this case this happens behind the 
scenes when invoking java.sql.Date.toLocalDate() but internally it just 
calls LocalDate.of(getYear() + 1900, getMonth() + 1, getDate()).

Now IMO the problem really is in java.sql.Date because it does a 
timezone conversion. The user who created the issue HHH-11396 
<https://hibernate.atlassian.net/browse/HHH-11396> pointed out he was 
using a DATE column type because he wanted to have a simple date i.e. 
year, month and date. When using java.sql.Date and the consumer is in a 
timezone after UTC i.e. UTC+1, the calculations of java.sql.Date will 
subtract that offset during /normalization/ and the millisecond value 
will change by that offset. This means that a date in the DBMS that is 
2000-01-01 will become 1999-12-31 when the client is in UTC+1.

One possible fix is to simply configure UTC for the consumer, then there 
will be no timezone shift.

I think what java.sql.Date does is wrong because a date has no time 
part, so there shouldn't be any time shifts. We should workaround that 
by shifting the millisecond value back when constructing a LocalDate.

What do you think should we do? Does anyone maybe know why java.sql.Date 
behaves that way?


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Mit freundlichen Grüßen,
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*Christian Beikov*