Time difference calculator

What is the time difference calculator?

A time difference calculator is a practical tool that allows users to quickly determine the time elapsed between two specific moments of the day or between two geographical regions located in different time zones. This calculator can be helpful for a wide range of activities, including travel planning, international business meetings, event scheduling, online gaming coordination, and even everyday uses such as measuring how long a task or activity has taken.

It supports both local time calculations (i.e., comparing two times within the same time zone) and time zone conversions (i.e., comparing times between selected cities around the world). The calculator can display results in hours, minutes, and seconds, offering precise and accurate measurements.

This tool uses the 24-hour time format, ensuring clarity and eliminating potential confusion that may arise from using 12-hour AM/PM notation.

Why is calculating time difference important?

Time differences play a crucial role in a globally connected world. Because the Earth’s rotation divides it into 24 standard time zones, communication across locations such as New York, Tokyo, London, or Sydney requires accurate time conversions.

For instance:

• A virtual meeting between participants in Los Angeles (UTC−08:00) and London (UTC+00:00) must account for an 8-hour difference.
• A traveler flying from New Delhi to Paris needs to note that New Delhi is in time zone UTC+05:30 and Paris is UTC+01:00, meaning the local time in Paris is 4 hours 30 minutes behind New Delhi time.

Understanding these differences avoids confusion, ensures punctuality in scheduling, and helps keep track of flight durations, deadlines, and live broadcasts.

Formula

The general formula for calculating the difference between two times in the same timezone is:

where:

• $T_1$ = starting time (in hours, minutes, seconds)
• $T_2$ = ending time (in hours, minutes, seconds)

If the calculation involves time zones, then we must include the offset associated with each:

where:

• $\Delta Z_1$ and $\Delta Z_2$ are the UTC offsets for each time zone (in hours and minutes),
• The result represents the total difference between the two local times.

Example of UTC Offsets:

• New York: UTC−05:00
• London: UTC+00:00
• Tokyo: UTC+09:00
• Sydney: UTC+10:00

When using cities, the calculator automatically applies the required UTC offset, including Daylight Saving adjustments, if applicable.

Examples

Example 1: Paris to London

Suppose you start work at 08:30:00 and finish at 17:15:00.

You worked for 8 hours and 45 minutes.

Example 2: Time difference across midnight

If one event occurs at 22:30:00 and the other at 02:15:00 (next day):

Since the second time is on the following day, we add 24 hours to $T_2$:

The total difference is 3 hours and 45 minutes.

Example 3: Time difference between time zones

Suppose it is 14:00 in London (UTC+00:00) and you want to know the time in Tokyo (UTC+09:00).

When it’s 14:00 in London, it’s 23:00 in Tokyo.

Example 4: Using city selection

If your meeting is scheduled at 10:00 AM in New York (UTC−05:00), and you need to know what time it will be in Paris (UTC+01:00):

The meeting in Paris will begin at 16:00 (4:00 PM) local time.

NOTES

• The calculator handles time wrapping around midnight automatically.
• When comparing two locations, daylight saving rules (DST) may affect the result — many cities apply a +1 hour adjustment during certain months.
• For precise measurements (e.g., in sports timing or scientific observations), seconds can also be included.
• Time differences are absolute values, meaning the order of subtraction doesn’t matter; only the span between two points in time is calculated.

Related concepts

Coordinated universal time (UTC)

UTC serves as the primary time standard by which the world regulates clocks. All time zones are expressed as positive or negative offsets from UTC (e.g., UTC−04:00 or UTC+10:30).

Daylight saving time (DST)

DST involves moving clocks forward by one hour during warmer months to extend evening daylight. This changes the time difference between zones temporarily.

Longitude and time

Each 15° of longitude corresponds roughly to one hour of difference in solar time. This relationship forms the basis for the Earth’s 24-hour division into time zones.

Frequently asked questions

How to calculate time difference?

Convert both times into total hours or minutes using the formula:

Then subtract the smaller value from the larger one. For example, between 14:45 and 09:20:

How many hours apart are London and Sydney?

London (UTC+00:00) and Sydney (UTC+10:00) differ by 10 hours, but during Daylight Saving Time, the gap may extend to 11 hours.

How to find local time in another city?

You can select both cities in the calculator — it adjusts for UTC offsets to give the corresponding time in the chosen destination. For example, if it’s 8:00 in Berlin (UTC+01:00), in Cape Town (UTC+02:00) it’s 9:00.

Why use 24-hour format instead of AM/PM?

The 24-hour format avoids ambiguity and improves consistency for international use, especially in aviation, military, computing, and global time conversion contexts.