I only noticed this because there happened to be a visit at the very end of one day's logs.
Old UA:
Mozilla/5.0 (compatible; SeznamBot/3.2; +http://fulltext.sblog.cz/)
New UA:
Mozilla/5.0 (compatible; SeznamBot/3.2; +http://napoveda.seznam.cz/en/seznambot-intro/)
It looks as if the change happened partway through 3 May, with an abrupt switch from old UA to new UA. And, as the URL implies, the new version includes information in English. I don't read Czech, so this is a big help. Amusingly, if you follow links, you'll find that pages accessible only from the new UA still list only the old UA, both for the primary spider and the “Screenshot-Generator" (their Preview). But I'm sure they'll sort it out in time.
I have always found Seznam a benign and inoffensive robot. Granted, the visitors they send can be counted on my fingers, but they seem to give reasonable responses to search queries (http, so you can see what the user was looking for).
