tidzoner

Tidzoner are regions of the Earth that share the same standard time, expressed as an offset from Coordinated Universal Time (UTC). The division into tidzoner is primarily based on longitude, with each hour corresponding to 15 degrees of longitude. In practice, political and practical considerations cause boundaries to deviate from exact meridians, so many tidzoner are irregular in shape. Offsets can be whole hours, but some regions use half-hour or even quarter-hour offsets, such as India (UTC+05:30) and Nepal (UTC+05:45).

Standard time is typically the local time within a tidzon. Many regions also observe daylight saving time (DST), shifting clocks by one hour during part of the year, though DST is not universally adopted.

UTC is the reference time used worldwide; national or regional authorities declare official time. The IANA Time Zone Database tracks the official zone rules for software and services, using region-based identifiers like Europe/Stockholm or America/New_York.

Historical development: The modern system emerged in the 19th century with railways; the Greenwich meridian was adopted as a global reference; the 1884 International Meridian Conference established a standard prime meridian and time zone concept. Since then, boundaries and offsets have changed due to political decisions.

Impact and applications: Time zones underpin scheduling, travel, broadcasting, finance, and computing. Changes to boundaries or DST rules can require updates to calendars and software; some regions have debated scrapping DST or altering offsets.