[Libreoffice-bugs] [Bug 117732] Firebird: Migration: Time values are being changed during migration process (data type TIME and DATETIME)

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=117732

--- Comment #29 from Alan Wheeler <ostersund18647 at gmail.com> ---
I had big problems with migrating dates in my BASE database until I deduced
that all dates that had been entered with a value that would have been in UK
Daylight Saving Time were out by 1 day after migration.

I got around this by creating and populating a table with three fields :-
Key field YEAR (as INTEGER) with values from 1916 to 2019
START_DATE (as DATE) containing the date of the start of DST for the year.
END_DATE (as DATE) containing the date of the end of DST for the year.

(Note that this table was complicated by the fact that the UK kept DST all year
during part of WW2 and from 1968 to 1970, so some end dates were 31st December
and some start dates were 1st January).

Then I wrote a macro to adjust all such dates in the remaining database tables
by 1 day in the opposite direction to the direction changed by the migration.

This worked perfectly, and I have now successfully migrated to Firebird, which
is definitely much faster than HSQLDB with JAVA.

I suspect that many users would have the skills to do something similar, but
most users wouldn't, so a method of automatically performing this adjustment
needs to be developed and incorporated into the migration.

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