David Patte <dpatte@relativedata.com> writes:
Zone Europe/London -0:01:15 - LMT 1847 Dec 1 0:00s
Does this mean that the city of London decreed that all clocks in the city of London should follow mean solar time with this pattern?
No, it merely means that common practice in London was to use local time before the stated date. Whether this was actually mean solar time, or some other approximation to mean solar time, isn't kept track of. The database currently approximates all the pre-standard-time stuff with local mean time (a.k.a. mean solar time a.k.a. mean time a.k.a. mean local time). London is very much a special case, since here LMT stands for "London Mean Time" as instituted by the Great Western Railway; this is valid for Great Western stations in London but not for all parts of London.
Does this also mean that all, or most towns around London also synchronized to London time on the same date, or should I assume that on this date each city & town around London was expected to synchronize to their OWN local mean times?
No, it's for London only. It doesn't say anything about locations other than London, for time stamps before 1970. The only claim is that all clocks in the Europe/London zone have agreed since 1970, and that the entry is accurate (as far it goes) for time stamps in London itself before 1970.
And what was the time-keeping standard before that date? I presume that many Brits where already using local mean times for their own towns before 1847, or should i assume that before 1847, most places in the UK where still using apparent solar times?
That's out of scope for the tz database. The actual situation was pretty chaotic (see the London example above) and is typically quite-poorly documented (London is one of the best-documented, and even so we don't at all know when each part of London switched).
- Also - before 1847, I am curious about two other calendar-related issues...
Calendar issues are out of scope as well; this is discussed in the Theory file.