Re: Why the high degree of granularity?
The original design of one hour time zones meant mean solar noon would be up to 1/2 hour from clock noon, if the boundaries were evenly spaced at 15 degree intervals.. Actual initial boundaries had some locations approaching 1 hour. Time zones creeping eastward have resulted in over 1 hour difference. Daylight savings time can bring this up to 2 hours. Then China went from 5 time zones to 1 time zone and you have an international boundary with Afghanistan with a 3 hour time change. By the time we accumulate 3600 seconds for a 1 hour change (about 7000 years), we could just skip the DST change in the appropriate direction, or non-DST locations schedule a time zone change.