Not against zones; I was hoping to shine a light on all the complexity around the TZDB, which is a mapping of zones to switchover times. Eg,

    $ zdump -v US/Eastern | grep 2020
    US/Eastern  Sun Mar  8 06:59:59 2020 UT = Sun Mar  8 01:59:59 2020 EST isdst=0 gmtoff=-18000
    US/Eastern  Sun Mar  8 07:00:00 2020 UT = Sun Mar  8 03:00:00 2020 EDT isdst=1 gmtoff=-14400
    US/Eastern  Sun Nov  1 05:59:59 2020 UT = Sun Nov  1 01:59:59 2020 EDT isdst=1 gmtoff=-14400
    US/Eastern  Sun Nov  1 06:00:00 2020 UT = Sun Nov  1 01:00:00 2020 EST isdst=0 gmtoff=-18000

If everyone simply picked a zone and stayed there, without the switching schedule above, you'd only need a mapping of zone to GMT offset and be done with it.