Indeed, people didn’t bother with time-zones until the invention of train time-tables. When passengers with watches got off trains in Bristol after a ride from London, they found the local clocks were “wrong”; of course they weren’t, they were just on local solar mean time while the watch was still on London solar mean time.
However, train companies found it more practical to have a standard time – if someone needs to switch the tracks to let one train turn off one way, after an earlier one came through from the other turning, they need to get the timing right, which is easier if they have a clock that’s synchronised with the clocks on both trains and the ones in the stations they come through.
So we invented time-zones in the 1800s so that the trains can run on time – or not, as the case may be, but at least whether or not they do is well-defined.

That lead to each country having a zone, some defined by a particular observatory’s solar mean time, others by offsets from one or another of those. Holland’s zone was 19 minutes, 32 and a bit seconds ahead of GMT.
In due course, as international travel and communication became more common, having the differences between zones easy to work with, so countries tended over time to set their zones in relation to GMT; eventually, a few complications with that lead to an international effort to define some more precisely-specified standards, meeting different requirements, including UTC as the replacement for GMT (which still gets used as if it were an alias for UTC).
In the course of that, of course, various jurisdictions have changed what offset from UTC they want to use, so their time zones have “transitions” arising from those changes; these either repeat an interval of time (only in the zone’s description, of course) or skip one and they complicate the life of this humble software engineer, who maintains software that has to correctly take those transitions into account, and get the necessary information from somewhere.

Daylight Saving Time, however, is sold as a way to make the most of such daylight as we do get – I can imagine it really is a kindness to some folk whose working hours are inflexible and oblige them to get up painfully early each day. The fact that there are tropical zones using it, however, baffles me.



Source link