HOW IT WORKS
This calculator shows the current time in two different time zones and calculates the exact time difference between them. Perfect for scheduling international meetings or calls. The time updates every second automatically.
UNDERSTANDING TIME ZONES
UTC (Coordinated Universal Time): The worldwide time standard. All time zones are defined as offsets from UTC (e.g., UTC+5:30 for India, UTC-5 for New York EST).
GMT (Greenwich Mean Time): Historically equivalent to UTC, but technically different. GMT is a time zone used in UK winter, while UTC is a time standard never affected by DST.
Why time zones exist: Earth rotates 360° in 24 hours = 15° per hour. Time zones roughly follow 15° longitude increments, but political boundaries often override geography. China uses one time zone despite spanning 5 theoretical zones.
Half-hour and 45-minute zones: Not all time zones are whole hours. India is UTC+5:30, Nepal is UTC+5:45, Australia (Adelaide) is UTC+9:30. These exist due to geographical or political reasons.
SCHEDULING GLOBAL MEETINGS
US-Europe (EST-CET): 6 hour difference. A 10 AM New York meeting is 4 PM in Paris/Berlin. Best meeting windows: 8-11 AM EST (2-5 PM CET) or 1-3 PM EST (7-9 PM CET).
US-Asia (PST-JST/CST): 16-17 hour difference (across date line). A Monday 6 PM LA meeting is Tuesday 11 AM Tokyo. Best window: 5-8 PM PST (next day 10 AM-1 PM Asia).
Europe-Asia (CET-IST/SGT): 4.5-7 hour difference. 10 AM Berlin = 2:30 PM Mumbai, 5 PM Singapore. Easier overlap than US-Asia.
Follow-the-sun workload: Global teams can work 24/7 by passing tasks across time zones: Sydney (start 9 AM) → London (start 9 AM = Sydney 7 PM) → New York (start 9 AM = London 2 PM) → San Francisco (start 9 AM = New York 12 PM).
DAYLIGHT SAVING TIME (DST) IMPACT
What is DST? Clocks move forward 1 hour in spring ("spring forward"), back 1 hour in fall ("fall back"). Goal: more daylight in evening hours during summer.
Who uses DST? Most of US/Canada (except Arizona, Hawaii), Europe, parts of Australia/New Zealand. Most of Asia, Africa, and South America do NOT use DST.
Time differences change twice per year: Example: London-New York is 5 hours when both observe DST, but 4 hours when only US is on DST (March-late March) or only UK is on DST (late Oct-Nov). Always verify actual current time, not just standard offset.
DST transition dates vary: US changes 2nd Sunday March/1st Sunday November. Europe changes last Sunday March/October. Australia changes 1st Sunday October/April (opposite season). These mismatches cause temporary unusual time differences.
TIME ZONE TOOLS & BEST PRACTICES
Use cities, not abbreviations: "EST" can mean Eastern Standard Time (UTC-5) or Eastern Summer Time (Australia, UTC+10). City names (America/New_York) are unambiguous.
Always include date when scheduling across zones: "3 PM Monday" is ambiguous if you're in different timezones. Use "3 PM Monday March 15 EST" or "15:00 UTC Monday March 15."
Calendar tools handle time zones: Google Calendar, Outlook automatically convert meeting times to each participant's local zone. Always set your device's time zone correctly.
Recording calls for global teams: If recording a meeting, announce the recording time in multiple zones so everyone knows when to watch replay.