Time Zone Converter
Convert times across world timezones with automatic daylight saving.
12:00 PM in America/New_York is 5:00 PM in Europe/London.
How It Works
The Time Zone Converter converts clock times between geographic regions using the official Internet Assigned Numbers Authority (IANA) time zone database.
Rather than relying on naive fixed UTC offsets (such as assuming London is always UTC+0 or New York is always UTC-5), EverydayNumbers evaluates exact daylight saving transitions for the specific calendar date chosen.
Formula & Calculation
UTC Instant Conversion Formula
All conversions route through an unambiguous UTC timestamp instant, preventing compounding rounding or calendar errors.
Dynamic Daylight Saving Time (DST) Handling
Because countries change clocks on different calendar dates (e.g. US in early March vs UK in late March), the time difference between two cities can vary by an hour depending on the date.
Step-by-Step Example
Example: New York (EDT) to London (BST) in Summer
Converting 12:00 PM on July 15 from New York to London:
America/New_York is in Daylight Time (EDT) = UTC−4→ UTC−412:00 PM + 4 hours→ 16:00 UTCEurope/London is in British Summer Time (BST) = UTC+1→ 16:00 UTC + 1 hour = 17:00 (5:00 PM)12:00 PM in New York corresponds to 5:00 PM in London on July 15 (a 5-hour difference).
Assumptions & Edge Cases
- IANA Named Zones vs. Fixed Abbreviations: Always use canonical IANA identifiers (e.g., "America/New_York", "Europe/London", "Asia/Tokyo"). Generic 3-letter abbreviations like "CST" are ambiguous because they can represent Central Standard Time (US), China Standard Time, or Cuba Standard Time.
- Date Boundary Crossings: When a time conversion crosses midnight, the tool displays an explicit "+1 day" or "−1 day" badge to alert users of date discrepancies in international meeting planning.
Frequently Asked Questions
Why does the time difference between London and New York change during the year?
The United States transitions to Daylight Saving Time on the second Sunday of March, whereas the United Kingdom and Europe transition on the last Sunday of March. For approximately two to three weeks each spring and autumn, the time difference temporarily shrinks from 5 hours to 4 hours.