From db60575bfbb6407dc93ca5d0f38cb2655fc4c54f Mon Sep 17 00:00:00 2001 From: Adriano dos Santos Fernandes Date: Thu, 5 Jul 2018 13:08:14 -0300 Subject: [PATCH] Add section "Updating the time zone database" to documentation. --- doc/sql.extensions/README.time_zone.md | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/doc/sql.extensions/README.time_zone.md b/doc/sql.extensions/README.time_zone.md index 20b9bffb45..ced7833281 100644 --- a/doc/sql.extensions/README.time_zone.md +++ b/doc/sql.extensions/README.time_zone.md @@ -317,6 +317,16 @@ Returns: 2018-10-21 03:00:00.0000 GMT 2019-02-17 01:59:59.9999 GMT -180 60 -120 ``` +# Updating the time zone database + +Time zones are often changed and when this happen it's convenient to update the time zone database as soon as possible. + +Firebird stores `WITH TIME ZONE` values translated to UTC time. If a value is created with one time zone database and later that database is updated and the update changes the information in the range of a stored value, when reading that value it will be returned as a different than the one initially stored. + +Firebird uses the [IANA time zone database](http://www.iana.org/time-zones) through the ICU library. ICU library present in Firebird kit (Windows) or present in OS (Linux, POSIX) sometimes has outdated time zone database. + +Update procedure is described in that [ICU page](http://userguide.icu-project.org/datetime/timezone#TOC-Updating-the-Time-Zone-Data). The easiest way to update is downloading the `*.res` files in a directory and set `ICU_TIMEZONE_FILES_DIR` to point to it. + # Appendix: time zone regions