Timezone Calculator
The Timezone Calculator converts any date and time between world timezones so you can coordinate supplier calls, shipment cutoffs, and handoffs across regions. Pick a source timezone and time, add one or more target timezones, and each converted local time — with its day, UTC offset, and business-hours status — appears side by side instantly.
Source Time
Detected from your browser — change it to convert from anywhere.
Comparing 2 timezones — shown under Converted Times.
Converted Times
Mon, Aug 3, 9:53 AM
Asia/Shanghai · UTC+8
Mon, Aug 3, 2:53 AM
Europe/London · UTC+1
Daylight saving is applied automatically for the selected date. Runs entirely in your browser — no API, works offline.
Formula
Target Local Time = Source Time − Source UTC Offset + Target UTC OffsetEvery timezone is defined by its offset from Coordinated Universal Time (UTC), which the calculator reads from the IANA timezone database built into your browser. Daylight saving transitions are applied automatically for the specific date you pick — a January call and a July call between the same two cities can differ by an hour. Conversion runs entirely on your device: no network requests, no API, and it works offline.
Variable Definitions
Source Timezone & Time
The timezone and wall-clock time you are starting from — e.g., 9:00 AM in Atlanta (US Eastern).
Target Timezones
One or more timezones to convert into — suppliers, carriers, ports, or colleagues. Add as many as you need to compare.
UTC Offset
Each zone's difference from UTC on the chosen date, including any daylight saving shift (e.g., US Eastern is UTC−5 in winter, UTC−4 in summer).
Example Calculation
Scenario: Your ocean carrier's documentation cutoff is 5:00 PM Friday at the port of Shanghai, and your logistics team sits in Chicago: - Source: Asia/Shanghai (UTC+8), Friday 5:00 PM - Target: America/Chicago (UTC−5 in summer) Shanghai is 13 hours ahead of Chicago in summer, so the cutoff lands at 4:00 AM Friday, Chicago time — meaning the shipping instructions actually have to be finalized by Thursday evening US time to make the vessel. Missing that window rolls the container a full week, which is exactly the kind of cutoff math this calculator is built to catch.
How to Interpret Your Result
• The "+1 day" / "−1 day" badge is the detail that catches most teams out: a Monday-morning call in the US is often already Monday evening — or Tuesday — in Asia. • The business-hours indicator flags whether the converted time lands inside a typical 9:00–17:00 workday in the target zone; use it to pick call times that are civil for both sides. • Offsets are date-specific. The US, UK, and EU change their clocks on different dates in spring and autumn, so recurring meetings can shift by an hour for a few weeks — re-check standing calls around late March and early November. • For shipment cutoffs, always confirm which timezone the cutoff is quoted in (port local time is common but not universal) before converting.