How accurate is the longitude/15 formula?

It is accurate for oceanic and remote regions but can be off by 30 minutes to 1.5 hours near political borders. Countries like India (UTC+5:30), Iran (UTC+3:30), and China (single UTC+8 across 5 geographic zones) are well-known exceptions.

Does this account for Daylight Saving Time?

No. The formula is purely geographic. During Daylight Saving Time, clocks in many regions advance one hour beyond the standard meridian offset. Always check a live time zone database (such as IANA tz data) if legal local time matters.

What coordinate format should I use?

Use decimal degrees. Latitude ranges from −90 (South Pole) to 90 (North Pole). Longitude ranges from −180 (International Date Line west side) to 180 (International Date Line east side). West longitudes are negative.

Why can the result be a half-hour offset like UTC+5:30?

While the standard formula produces whole-hour offsets, some countries officially observe half-hour or quarter-hour offsets. This tool shows the whole-hour approximation but notes that half-hour zones exist nearby.

What is the UTC offset range?

Geographic UTC offsets range from UTC−12 (far west of the date line) to UTC+12 (far east). In practice, inhabited legal time zones span UTC−12 to UTC+14, but the longitude formula caps at ±12.

Timezone From Coordinates

Name: Timezone From Coordinates
Availability: InStock
Author: Nham Vu

Enter a latitude and longitude to estimate the UTC offset based on the geographic meridian, with notes on DST and political boundary exceptions.

Enter Coordinates

Latitude (decimal degrees, −90 to 90)

Longitude (decimal degrees, −180 to 180)

Try an example

Enter coordinates and click "Estimate Timezone" to see the UTC offset.

Summary

Enter a latitude and longitude to estimate the UTC offset based on the geographic meridian, with notes on DST and political boundary exceptions.

How it works

Enter a decimal latitude (−90 to 90) and a decimal longitude (−180 to 180).
The tool divides the longitude by 15 and rounds to the nearest integer to get the estimated UTC offset.
The estimated offset is displayed along with the probable UTC label (e.g. UTC+5 or UTC−3).
A breakdown shows the raw calculation so you can understand the approximation.
A disclaimer reminds you that political boundaries and DST may shift the actual legal offset by ±0.5 to ±1 hour.

Use cases

Quickly estimate a time zone when only GPS coordinates are available.
Cross-check coordinate data against expected time zones in GIS workflows.
Teach or demonstrate how the 24-meridian time zone system works.
Estimate UTC offset for a remote location before more precise lookup is possible.
Pre-flight checks for drone or field operations where network access is limited.
Validate exported coordinate records that include a UTC offset field.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu