Time zones
Why do governments change time-zone rules?
Civil time is law and policy. A government can change an offset, daylight-saving schedule or boundary when it decides the practical benefits outweigh the disruption.
Clocks serve public life
Governments set civil time for their jurisdictions. Changes can be driven by trade, travel, energy policy, regional coordination, administrative convenience or political decisions. There is no single worldwide authority that can prevent a country changing its rule.
The difficult part is the notice
A new rule affects airline systems, calendars, payroll, broadcasting and ordinary meetings. Even a well-intentioned change can break future appointments if phones and servers have not received updated data by the time it takes effect.
Why WorldTime uses named zones
The IANA database is updated when political bodies change boundaries, offsets and daylight-saving rules. A named zone gives this site a route to the new rule; a hard-coded difference between two cities does not.