[tz] Rules for TZ+ database

Lester Caine lester at lsces.co.uk
Thu Sep 5 18:58:31 UTC 2013

Guy Harris wrote:
> ...and do items in the timeline have time stamps for entries created before Facebook existed or do they just have dates?  If they just have dates, then Facebook, at least, won't care.  If they have times, are they represented as something such as a UTC-based seconds-{before,since}-the-Epoch or are they represented as local time (so that if the user starts their timeline with "Born on March 4, 1957, at 4:27 PM", that's how it's reported to all Facebook users, regardless of what time zone they're in).

If we were just typing in raw information, then there would not be a problem, 
but having gathered growing volumes of data which includes a lot of accurate 
time material then normalizing the data to UTC is the next stage to ensure 
events are correct chronologically across time zones. If the calendar of events 
is correct in 1970 it should also be connect in 1969 and any year before. My 
first experience of this was with RECENT calendars where meetings were getting 
scheduled wrong 6 months later because one application was not bothering with 
daylight saving and another was ... even though both were storing as UTC. Some 
of my customers are looking to load archive data beyond the 20 years history we 
already have and that will go back past 1970, so how do I ensure that 
normalization of 1970 data will match 1969 stuff?

Even just timelining all the material I have related to creating the TZ data 
needs to have correctly managed offsets for the timeline.

Lester Caine - G8HFL
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