About Time Zones
Time zones are regions of the Earth that observe a uniform standard time. There are 24 primary time zones, each roughly 15 degrees of longitude apart. However, many regions have adopted half-hour or quarter-hour offsets from Coordinated Universal Time (UTC).
UTC (Coordinated Universal Time)
UTC is the primary time standard by which the world regulates clocks. Time zones are expressed as positive or negative offsets from UTC. For example, EST (Eastern Standard Time) is UTC-5, meaning it is 5 hours behind UTC.
Daylight Saving Time (DST)
Many regions observe Daylight Saving Time, shifting clocks forward by one hour in spring and back in fall. This can affect time differences between locations. Not all countries observe DST, and the dates vary by region.
Common Time Zone Abbreviations
- PST/PDT: Pacific Standard/Daylight Time (UTC-8/-7)
- MST/MDT: Mountain Standard/Daylight Time (UTC-7/-6)
- CST/CDT: Central Standard/Daylight Time (UTC-6/-5)
- EST/EDT: Eastern Standard/Daylight Time (UTC-5/-4)
- GMT/BST: Greenwich Mean Time/British Summer Time (UTC+0/+1)
- CET/CEST: Central European Time/Summer Time (UTC+1/+2)
- IST: India Standard Time (UTC+5:30)
- JST: Japan Standard Time (UTC+9)
Tips for International Scheduling
- Use UTC as a common reference when coordinating across many time zones
- Consider business hours in all participating time zones
- Be aware of DST transitions which can temporarily change time differences
- Use calendar apps that automatically handle time zone conversions