WorldTime Grid
Time Calculation Methodology
Technical explanation of IANA zones, UTC conversion, daylight saving calculations and known limits.
1. Purpose and scope
WorldTime Grid performs the main calculation in the browser. The selected cities are represented by IANA time-zone identifiers, and the chosen local date is converted to one UTC instant before it is rendered for every participant. This prevents chains of local-to-local arithmetic and preserves date-specific daylight-saving behavior.
Planner preferences such as favorite cities, order, working hours, time format and meeting duration may be stored in localStorage on the same device. No account is required and these preferences are not sent to a WorldTime Grid database. A reset control removes the stored planner value.
2. How the browser tool handles data
A share link can include selected zones, date, chosen instant, duration and display format. It is intentionally designed not to require names, email addresses, confidential titles or meeting links. Anyone who receives the URL can see the scheduling information embedded in it, so users should still review the query string before sharing.
Calendar files are generated locally with UTC start and end values. User-provided text is escaped before it enters the ICS document. Calendar applications remain responsible for showing the event under the recipient's own settings, and organizers should reopen the exported file before sending an important invitation.
3. Accuracy and limitations
Time-zone rules are political data and may change. Browser and operating-system releases can contain different versions of the IANA database. WorldTime Grid therefore presents results as planning assistance, displays transition warnings where possible and recommends final verification in participant calendars.
The site does not promise that a convenience score is an objective measure of human wellbeing. Labels such as Best, Good, Possible and Poor are simple interpretations of editable working-hour assumptions. Fairness should also be reviewed across a series of meetings, not only one event.
4. Your choices and responsibilities
Optional advertising services may use cookies or similar technologies only under the consent choices presented to the visitor. The privacy and cookie pages explain how to review or change those choices and how browser-stored preferences can be removed.
Editorial pages are written to answer a distinct scheduling question rather than to create thousands of city-pair doorway pages. Corrections should identify the affected page, date, zone and source. Substantive corrections should update the review date and, when useful, explain the change.
Last updated: 2026-06-30