Time Zone Converter
Enter a source hour in 24-hour format and the UTC offset difference between the two time zones to find the equivalent local time at the destination. Perfect for scheduling international calls, meetings, and travel logistics.
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Calculator
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Formula
Target = (Source + Offset) mod 24
Adding the offset to the source hour gives the raw target hour, which may be outside the 0-23 range for very early or late times. Subtracting 24 × floor(raw/24) is equivalent to modulo 24, wrapping the result back into the 0-23 hour range. Positive offsets move the time forward; negative offsets move it back.
How to use the Time Zone Converter
- 1
Enter your source hour (0-23)
- 2
Enter your time zone offset (hours, e.g. -5 for est)
- 3
Read your results instantly
Results update in real time as you type.
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Understanding UTC Offsets
Coordinated Universal Time (UTC) is the global time reference. Every time zone is expressed as an offset from UTC: New York (EST) is UTC-5, London (GMT) is UTC+0, Paris (CET) is UTC+1, Dubai is UTC+4, Tokyo is UTC+9. To convert New York time to Tokyo time, the offset is +14 (Tokyo is 14 hours ahead of New York during Eastern Standard Time). Daylight Saving Time shifts some zones by ±1 hour — be sure to check the current offset when DST is in effect.
Daylight Saving Time Complications
Over 70 countries observe Daylight Saving Time (DST), but not all on the same schedule. The US moves clocks forward in March and back in November. Europe changes in late March and late October. Arizona (US) and most of Asia and Africa do not observe DST at all. During transition weeks, the offset between two DST-observing zones stays the same, but the offset between a DST zone and a non-DST zone changes. Always double-check the current UTC offset before scheduling critical international meetings.
Tips & Insights
Use UTC as a Universal Reference
When scheduling across multiple time zones, share the meeting time in UTC (e.g., '15:00 UTC') and let each participant convert to their local time. This eliminates confusion about who is accounting for DST.
World Clock Apps for Multiple Zones
For regular cross-timezone communication, a world clock app or website like timeanddate.com shows dozens of zones simultaneously and handles DST automatically.
Positive vs. Negative Offsets
To go from New York to Paris, Paris is 6 hours ahead (UTC+1 vs. UTC-5), so offset = +6. To go from Paris to New York, offset = -6. Always think 'how many hours does the destination add or subtract from source?'
Worked Examples
Noon New York to London (offset +5)
17:00 (5 PM) in London.
9 AM Tokyo to New York (offset -14)
19:00 (7 PM) previous day — shown as 19 in 24h.
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Frequently Asked Questions
What is a UTC offset?
A UTC offset is the number of hours a time zone is ahead of or behind Coordinated Universal Time. EST is UTC-5, meaning 5 hours behind UTC. Tokyo is UTC+9, meaning 9 hours ahead.
How do I find the offset between two cities?
Subtract city A's UTC offset from city B's UTC offset. New York (UTC-5) to London (UTC+0): 0 - (-5) = +5. Enter +5 as the offset when converting New York time to London time.
What happens when the result is over 23?
The formula wraps it back to 0-23 automatically. A raw result of 26 becomes 2 (26 - 24 = 2), representing 2:00 AM the next day.
Does this handle half-hour time zones?
Yes. India (IST) is UTC+5.5. Enter 5.5 or -5.5 as the offset. The calculator handles decimal offsets for zones like India, Iran, and Australia/Adelaide.
How do I account for Daylight Saving Time?
Manually adjust the offset by +1 when your source time zone is on summer time (DST). For example, New York in summer is UTC-4, not UTC-5.
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