Pre-Fleming Calendrical Database

David Patte dpatte at
Tue Mar 30 01:26:14 UTC 2010


Much of this is probably off topic, and may be wordy for many of the 
people on this list, but I have some questions about the historical 
meanings within the tz files, and how the files could be extended 
backwards for further date/time studies before 1980 & 1847.

Perhaps my questions should be directed to calendar historians within 
this list, but here's what's on my mind..

- I am particularly interested in the meaning and accuracy of the 
opening entries for each tz zone. Almost every zone starts with an LMT 
record. For example, For Europe/London, the opening record states:

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? 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?

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?

For example: if I am researching Canterbury, on what date should I 
assume that it would start following its own LMT, and on what date would 
it start following London's LMT: before 1847, 1847, or later?

Its easy enough to determine a location's apparent solar time, but 
determining when a place moved from apparent solar time to mean solar 
time, or then to a regional tz-based mean solar time is not clear to me.

- Also - before 1847, I am curious about two other calendar-related 

1) For each tz zone, on what date did a preferred or decreed calendar 
change? (julian, gregorian, islamic, Chinese, French Republican, etc.). 
Most Catholic zones moved to Gregorian originally, but non-Catholic 
zones move to Gregorian on their own decreed dates.

2) For each zone, on what date did the start of year change? (Jan 1st vs 
March 1st, for example).

The above issues are important to me for comparative historical studies, 
and genealogy.

I intend to starting keeping track of the these pre-Fleming calendrical 
rules - yet using tz's zone names for synchronization - and making it 
freely available for others if it has not already been done. I'm willing 
to take it offline of this list and maintain it myself and for others 
for free download.

Would there be other people on this list, or calendar historians, that 
would also be interested in me keeping this information in a usable 
standard format, and would people be interested in providing data, 
references and updates for a pre-tz calendrical preferences database 
like that I've mentioned above?

Feel free to reply to me off this list, or on, whichever is most 
appropriate. I'm also willing to start a separate mailing list if its 


David Patte
Relative Data, Inc.

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