How the conversion works
Every time zone is described by its offset from Coordinated Universal Time (UTC). To convert a clock reading from one zone to another, you only need the difference between their offsets: the calculator adds (destination offset minus source offset) hours to the original time. If New York is UTC-5 and Tokyo is UTC+9, the difference is 14 hours, so 12:00 in New York becomes 02:00 the next day in Tokyo.
Adding or removing hours can push the clock past midnight, so the tool also tracks whether the date moved forward or back and reports the day change alongside the converted time.
Reading the day change
Because the world spans more than 24 hours of offset, a converted time frequently lands on a different calendar day. The "Day change" line tells you whether the result is the same day, the next day, or the previous one, and the note spells out the exact converted date.
This matters for scheduling: a 9:00 AM meeting in one zone might be late evening the day before in another, so always check the date as well as the time before confirming.
Daylight saving and other caveats
The biggest limitation is daylight saving time. This tool uses the fixed whole-hour offset you choose and does not shift automatically for summer time.
- During a DST period, pick the offset actually in effect — for example UTC-4 for New York in summer rather than its standard UTC-5.
- Offsets here move in whole hours; a few zones use 30- or 45-minute offsets that this list does not cover.
- Zone boundaries and DST rules change over time and by country, so for legal or travel-critical times confirm against an authoritative source.
- The conversion is purely arithmetic on the offsets you select.
Formula
convertedTime = time + (toOffset − fromOffset) hoursFrequently asked questions
- Does this handle daylight saving time?
- No. It uses the fixed UTC offset you select, so during a DST period choose the offset in effect (for example UTC-4 for New York in summer).