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Date, Time & Age

Time Zone Conversion Calculator

Convert a date and time between IANA time zones with daylight-saving rules applied, and detect nonexistent or ambiguous local times.

Your inputs

Results

Time in Europe/London

2026-07-01 17:00

UTC
2026-07-01 16:00
Offset of America/New_York
UTC−04:00
Offset of Europe/London
UTC+01:00
Difference
+5 h
Calendar day change
Same day
Local time status
Valid

✓Exact calculation — rounded only for display

Notes for this result

  • Uses your browser’s IANA time-zone database, which includes historical and announced daylight-saving rules.

What this calculator does

Time zone offsets change with daylight saving, and rules differ by country and year. This tool uses the browser’s IANA time zone database to convert correctly.

Formula and method

Local time in zone A → UTC instant (checking candidate offsets before and after the date) → local time in zone B.

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Date and time: 2026-07-01T12:00
  • In time zone: America/New York
  • Convert to: Europe/London

Results

  • Time in Europe/London: 2026-07-01 17:00
  • UTC: 2026-07-01 16:00
  • Offset of America/New_York: UTC−04:00
  • Offset of Europe/London: UTC+01:00
  • Difference: +5 h
  • Calendar day change: Same day

How to read the results

During a spring-forward gap, some local times never happen; during fall-back, some happen twice. Both cases are reported.

Assumptions and limitations

  • Accuracy depends on the time zone data in your browser, which is updated with your operating system and browser.

Questions

Why use city names instead of EST or GMT?

Abbreviations are ambiguous and do not encode daylight-saving rules; IANA zone names do.

Methodology and verification

Result type
Exact mathematical calculation (rounded only for display)
Formula version
1.0
Automated verification
6 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

Privacy

Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Inputs are added to a share link only if you choose to include them. Privacy policy