While fixing QTBUG-52284, integration [0] ran into one transition in one zone failing. Closer examination reveals a bug in the TZ database in use on Linux,
misdescribing Europe/Samara's transitions in 2010. According to [1], the 2010-03-28 transition changed the standard offset while starting DST, leading to no change in the actual offset; the 2010-10-31 transition ended DST normally. (The following March saw another standard time offset, this time without DST, and there have been no transitions since.) However, the TZ database describes the 2010-03-28 transition as putting the zone's standard offset at UTC+4 with no DST. This leads to the 2010-10-31 being a fall-back without a DST change, which there is no way to disambiguate when mapping back from zone time to UTC.

• [0] https://codereview.qt-project.org/162414
• [1] http://www.timeanddate.com/time/zone/russia/samara

This bug report exists to track the need to report this error to the upstream TZ database and record what results.