[toast0]

Timezone aware code already has to process 15 minute timezones, IIRC; India is on a 30 minute timezone.

Some timezone changes are well published before the change and others are published after, and software has to pick up the pieces.

I'd imagine a 15 minute jump to recenter zones would be published with at least as much notice as changes to DST rules.

[hermitdev]

AFAICT from looking at the source for the tz database [0], it's capable of handling UTC offsets at least to a second level, if not fractional seconds.

[0] https://github.com/eggert/tz

[fanf2]

ISO 8601 and other display standards for timezones only support one minute resolution.