How do I calculate the time between two times across midnight?

Enter the start time and the end time and choose “on the next day”. From 23:50 to 00:10 is then 20 minutes. With “on the same day”, an earlier end time is shown as an error. Choose “on the next day” for this calculation.

Are identical times 0 or 24 hours apart?

It depends on the chosen day. From 00:00 to 00:00 on the same day is 0 hours; on the next day it is 24 hours. Enter 00:00 instead of 24:00 and set the day of the end time.

Can I subtract a break and read the result in decimal hours?

Yes. In “Time between”, the break you enter is subtracted from the time between. 8 hours and 30 minutes minus a 30-minute break is 8 hours, that is 8.00 decimal hours. Statutory breaks and pay are not calculated. The decimal display is rounded: one minute is shown as 0.02 hours, not 0.01 hours.

Why is daylight saving time not taken into account?

The actual elapsed time needs a date and a time zone. Where daylight saving time applies, the actual time from 01:30 to 03:30 on a changeover day can be one hour or three hours. A pure clock-time calculation gives two hours in both cases. Some clock times are skipped or occur twice on a changeover day. Because this calculator does not ask for calendar dates, it does not calculate an actual duration across a daylight saving changeover.

Are my inputs or results saved?

Calculations run in your browser. semku does not send the inputs and results of this calculator to the server and does not save them in browser storage. For “Undo”, the state before the reset is kept temporarily in memory. It is discarded on new input, a changed selection or when you leave the page. Copied text can remain in your clipboard. This page sends usage statistics and automatic error reports, but they do not include the times you enter or the results. See “Privacy on this page”.

Time calculator

Calculate the time between two clock times, or add and subtract hours, minutes and seconds.

Calculation

Time between Add time Subtract time

Start time time Format: 09:30 or 09:30:15. The field follows your browser’s clock format (12- or 24-hour); results are shown on a 24-hour clock. Without seconds, 00 seconds is used. Times from 00:00 to 23:59:59 are accepted.

End time time

The end time is

on the same day on the next day

—

Your inputs are kept when you switch. Results are not copied into the input fields automatically. Choose whether the end time is on the same day or on the next day. “On the next day” means the following calendar day, so the time between can be more than 24 hours.

Calculation rules and supported inputs

The calculator uses clock times without a date. An hour has 60 minutes, a minute has 60 seconds and a calculation day has exactly 24 hours. Your browser’s time zone does not affect the result.

For the time between, the start time is subtracted from the end time. If the end time is on the next day, 24 hours are added before subtracting. Identical times therefore give either 0 or 24 hours. More than 24 hours is possible too: from 09:00 to 10:00 on the next day is 25 hours. Only the same day and the next day can be chosen.

“On the same day” is the default. If the end time is earlier, choose “on the next day” or correct the times. The chosen day is kept when you change the times.

A break you enter is subtracted once from the time between. Empty break fields count as 0. The break cannot exceed the time between. Statutory breaks are not subtracted automatically; working-time rules and pay are not checked.

When adding or subtracting, the duration you enter is added to or subtracted from the start time. The result always shows the clock time and how many days it lies before or after the start day. For example, 23:30 plus 2 hours and 45 minutes is 02:15 on the next day.

Clock times run from 00:00 to 23:59:59. 24:00 is not accepted as a time; for an end at midnight, use 00:00 and the next day. A duration of 24 hours is allowed. The duration can be up to 999,999 hours, 59 minutes and 59 seconds. Negative inputs, fractions of a second and decimal hours as input are not supported.

Internally, the calculation uses whole seconds. Decimal hours are calculated by dividing the seconds by 3,600. Only the display is rounded to two decimal places, rounding half up. One minute is shown as 0.02 hours. This rounded number is not used in further calculations. The display in hours, minutes and seconds stays exact.

The calculator does not determine the actual elapsed time between calendar dates and does not convert between cities or time zones. Daylight saving time, leap seconds and legal working-time or pay rules are not taken into account.

Calculation rules v1 · 2026-09-18

Frequently asked questions

How do I calculate the time between two times across midnight?: Enter the start time and the end time and choose “on the next day”. From 23:50 to 00:10 is then 20 minutes. With “on the same day”, an earlier end time is shown as an error. Choose “on the next day” for this calculation.
Are identical times 0 or 24 hours apart?: It depends on the chosen day. From 00:00 to 00:00 on the same day is 0 hours; on the next day it is 24 hours. Enter 00:00 instead of 24:00 and set the day of the end time.
Can I subtract a break and read the result in decimal hours?: Yes. In “Time between”, the break you enter is subtracted from the time between. 8 hours and 30 minutes minus a 30-minute break is 8 hours, that is 8.00 decimal hours. Statutory breaks and pay are not calculated. The decimal display is rounded: one minute is shown as 0.02 hours, not 0.01 hours.
Why is daylight saving time not taken into account?: The actual elapsed time needs a date and a time zone. Where daylight saving time applies, the actual time from 01:30 to 03:30 on a changeover day can be one hour or three hours. A pure clock-time calculation gives two hours in both cases. Some clock times are skipped or occur twice on a changeover day. Because this calculator does not ask for calendar dates, it does not calculate an actual duration across a daylight saving changeover.
Are my inputs or results saved?: Calculations run in your browser. semku does not send the inputs and results of this calculator to the server and does not save them in browser storage. For “Undo”, the state before the reset is kept temporarily in memory. It is discarded on new input, a changed selection or when you leave the page. Copied text can remain in your clipboard. This page sends usage statistics and automatic error reports, but they do not include the times you enter or the results. See “Privacy on this page”.

Privacy on this page

Calculations run in your browser. The times you enter and the results are not sent to the server or saved in browser storage. The state kept for “Undo” exists only in temporary memory; reloading the page returns the inputs to their initial state.

To understand how the page is used and to improve the service, this page sends semku’s own usage statistics and automatic error reports. They go only to the dedicated endpoint under semku.com/api/telemetry/v1/. They are not used for advertising or third-party tracking.

The usage statistics include the stage of use (such as starting an operation or requesting a copy), the time it happened and fixed identifiers that distinguish the page and feature. They do not include the times you enter, the results shown or the text you copy. Inputs are not sent as hashes or as size categories either. The full URL and search terms are not sent.

Operations and sessions are distinguished by randomly generated identifiers. In the browser these exist only in temporary memory and are not written to cookies or browser storage. No identification based on cookies or combined device characteristics is used.

Error reports contain the error type, code and time, and, where available, a registered program-source identifier with the line and column number. The error message text and stack traces are not sent. Usage statistics and error reports also carry the site identifier, the published build and a random record identifier. IP addresses and user-agent strings are not part of these items.

The feedback form sends the rating you chose and the text you typed in the free-text field when you press the send button. A random ID that distinguishes the submission, the page, site and published build, and the type of request are also sent. There are no fields for your name, email address or phone number, and the times you enter are not attached automatically. Whatever you write in the free-text field is sent as is. Please do not enter personal data, passwords, authentication keys or payment details.

Separately, when you visit the site, the hosting provider records your IP address, the time of the request and user-agent information about your browser and device in Cloudflare Pages’ standard access logs.

For details, see the privacy policy in Korean.

Calculations run in your browser without sending your times or results to the server. See “Privacy on this page” for information about access data.