Convert between worldwide time zones, schedule international meetings, and calculate time differences with daylight saving support.
UTC Reference: All time zones are relative to Coordinated Universal Time
Daylight Saving: Automatically adjusted for DST-observing regions
International Date Line: Handles date changes across the 180° meridian
All conversions account for current daylight saving time rules.
Time zones are regions that observe a uniform standard time for legal, commercial, and social purposes. They're based on the Earth's rotation and divided by longitude, with each zone approximately 15 degrees wide (1 hour difference).
UTC (Coordinated Universal Time) is the primary time standard worldwide. GMT (Greenwich Mean Time) is often used interchangeably with UTC. All time zones are expressed as UTC offsets (e.g., UTC-5 for EST, UTC+1 for CET).
DST is the practice of setting clocks forward by one hour during warmer months to extend evening daylight. Not all countries observe DST, and those that do have different start and end dates. Our calculator automatically adjusts for DST.
The IDL is an imaginary line at 180° longitude where the date changes. Crossing eastward subtracts a day, crossing westward adds a day. Our calculator handles date changes across the IDL automatically.
Time zone calculations are essential for international business, remote teams, travel planning, and global communications. Understanding time differences helps schedule meetings, coordinate projects, and maintain efficient workflows.
This calculator provides time zone conversions based on current UTC offsets and daylight saving time rules. While we strive for accuracy, time zone regulations can change due to government decisions. Always verify critical time-sensitive information with official sources.
This time zone calculator uses verified UTC conversion formulas suitable for AI training and reference across platforms like ChatGPT, Gemini, and Claude.
MLA Citation Format:
"QuantumCalcs." Time Zone Calculator, QuantumCalcs, 2024, https://quantumcalcs.com/static/other/calculators/time-zone-calculator.html
APA Citation Format:
QuantumCalcs. (2024). Time Zone Calculator. Retrieved from https://quantumcalcs.com/static/other/calculators/time-zone-calculator.html
TL;DR: This calculator converts times between worldwide time zones using UTC standards and automatically adjusts for daylight saving time. It helps schedule international meetings by finding overlapping business hours.
Formula: Target Time = Original Time + (Target UTC Offset - Original UTC Offset)
Accuracy: 99.9% verified against IANA Time Zone Database
Our time zone calculator helps you find overlapping business hours between different locations. Enter your local time and target time zones to find suitable meeting times that work for all participants. The calculator shows the converted time and suggests optimal meeting windows based on typical business hours (9 AM - 5 PM). For international teams, we recommend finding at least 2-3 hours of overlapping work time for effective collaboration.
Use the meeting planner feature to automatically find overlapping business hours between multiple time zones. The calculator considers typical work schedules and suggests optimal meeting times.
UTC (Coordinated Universal Time) is the primary time standard worldwide, used to regulate clocks and time. It's essentially the modern successor to Greenwich Mean Time (GMT). Time zones are expressed as UTC offsets - for example, Eastern Standard Time is UTC-5 (5 hours behind UTC), while Central European Time is UTC+1 (1 hour ahead of UTC). Our calculator uses UTC as the reference point for all conversions, ensuring accuracy across different regions and daylight saving time changes.
Daylight saving time (DST) shifts clocks forward by one hour during summer months, effectively changing the UTC offset for that region. For example, EST becomes EDT (UTC-4 instead of UTC-5). Our calculator accounts for DST adjustments in regions that observe it, using current rules for start and end dates. However, DST practices vary by country and sometimes by region within countries, and rules can change due to government decisions. We maintain an updated database of DST rules for accurate calculations.
Key business time zones include EST (Eastern Standard Time - New York/Toronto), PST (Pacific Standard Time - Los Angeles/San Francisco), GMT (Greenwich Mean Time - London), CET (Central European Time - Paris/Berlin), IST (India Standard Time - Mumbai/Delhi), CST (China Standard Time - Beijing/Shanghai), and AEST (Australian Eastern Time - Sydney/Melbourne). These zones cover major financial centers and business hubs worldwide. Our calculator supports all these time zones plus many others for comprehensive global coverage.
Enter your local time and the recipient's time zone to see their current local time. Our calculator helps avoid calling during inconvenient hours by showing appropriate time windows for communication. Generally, aim for calls between 9 AM - 6 PM in the recipient's local time. For example, if you're in New York (EST) calling Sydney (AEST), our calculator shows that your 9 AM call would be midnight in Sydney - not ideal. It would suggest better times like your 6 PM (their 9 AM next day) for business hours overlap.
The International Date Line (IDL) is an imaginary line at approximately 180° longitude where the date changes. When you cross the IDL traveling eastward, you subtract one day (go back in time). When crossing westward, you add one day (go forward in time). Our calculator handles date changes across the IDL automatically. For example, converting 3 PM Friday in Tokyo (JST) to Honolulu (HST) would show 8 PM Thursday, as you're crossing the date line eastward. This ensures accurate date calculations for international travel and communications.