Political boundaries override geography
Ideal time zones would be 24 vertical strips, each one hour apart. Instead, political boundaries, national unity, and economics drive many deviations. China spans five geographic time zones but uses one national standard. India uses +5:30 (half-hour offset) for historical and political reasons. Nepal uses +5:45 (quarter-hour offset). These oddities are deliberate political choices, not geographic necessity.
Daylight saving and global coordination
About 70 countries observe daylight saving time (DST), shifting clocks forward in summer. But the dates vary: the US, Europe, and other regions switch on different weekends, creating brief periods where they are misaligned. This complicates global coordination, especially for finance and logistics. Some countries have abandoned DST due to the disruption it causes, and scientific evidence questions whether DST saves energy. Time zone complexity is political and historical, not purely geographic or efficient.