Is there a known special problem for Europe/Kaliningrad? My code and the HowardHinnant date library agree on this transition. The TZ database says:

Zone Europe/Kaliningrad

 2:00   Russia  EE%sT   2011 Mar 27  2:00s

Rule    Russia  1984    1995    -       Sep     lastSun  2:00s  0       -      
Rule    Russia  1985    2010    -       Mar     lastSun  2:00s  1:00    S

So, on Mar 26, 1989:

* at 1:59, Kaliningrad is on UTC+3 (SAVE=0)

* at 2:00s (which is identical to 'w' in this case, because we need to use the STDOFF of the transition immediately to the left), Kaliningrad switches to UTC+2+{SAVE}

* but the Russia rule also takes effect at 2:00s, so SAVE becomes +1

* so Kaliningrad switches to UTC+2+1, i.e. remains at UTC+3

* Kaliningrad clock stays at 2:00

I think the key here is that both the Zone entry and the Rule entry use the same "2:00s", which are both interpreted using the STDOFF of the transition immediately to the left of the 2:00s.

I don't know the internal details of the HowardHinnant's date library, but my code normalizes the various transition times to 'w' time, so the above explanation is only a rough translation of what the code actually does. The other interesting question is what happens on Sept 24, 1989, when it reverts back to STD time at 2:00s. Both my code and HowardHinnant date library seem to correctly convert the 2:00s to 3:00w, and the clock goes from 2:59 -> 2:00.

Brian