Lester Caine wrote:
having a single repository for ALL available data should be a goal?
Sure, it's a worthy goal, even if pre-1970 timestamps are currently out of scope for the current database. We could collect all the data that we can for an extended database that contains new zones that differ from existing ones only for pre-1970 timestamps. We could then derive the current database by applying a filter to the extended database, along the lines that Zefram suggested. This filtering could be done automatically and at the source level, so existing tz source file readers would not need to be changed, and we wouldn't have to maintain two copies of the database. As I understand it, Stephen wouldn't oppose the existence of a filter per se, but is uneasy about having the default filter being set to 1970. But I'm afraid the filtering approach won't work unless we continue to filter at 1970 as we have regularly done in the past. Too much existing practice is based in the 1970 cutoff, and (as now explained in the Theory file) the 1970 cutoff is not really that arbitrary -- rather, it corresponds roughly with the advent of computerized timekeeping and of a greater need for standardized civil time.
I probably need to point out that as far as I am concerned, the UK data is correct back to the creation of daylight saving back in 1916
I think you're right, but the UK is quite a special case: the tz database relies on years of first-class work done by Joseph Myers and others. Other countries are not done nearly as well. And even the UK entries, which are the best we have, don't cover all the history of standard time in the UK, much less pre-standard time. For more about this, please see Myers's nice summary <http://www.polyomino.org.uk/british-time/>.