When clocks change,
count the time that passes.

What this calculator handles

Ordinary subtraction from 22:00 to 06:00 gives eight hours. That is the difference between the displayed clock readings. If clocks go back during that interval, nine actual hours pass. If they go forward, seven hours pass. This calculator shows both measures and identifies the difference.

Each local date and time must first identify an instant. The first 02:30 during daylight time and the second 02:30 during standard time are different instants. A fall-back input therefore asks you to choose the first or second occurrence; the calculator does not guess on your behalf.

One clock reading, two different instants

A full hour passes from the first 02:30 to the second 02:30, although the clock shows the same digits. Spring has the opposite problem: 02:30 on March 29, 2026 does not exist in Berlin. Choose a real time before or after the clock jumps forward.

Berlin and New York are not always six hours apart

Germany ends daylight saving on October 25, 2026; New York changes on November 1. During the intervening week, ordinary daytime meetings have a five-hour difference instead of six. Recalculate each date of a recurring meeting. The “one week later” preview preserves the local source time, not a fixed UTC instant.

Using the result

Select a time zone and complete start and end dates. If an entry is ambiguous, two possible UTC instants appear. Choose one before expecting a unique duration. Break minutes are subtracted from actual elapsed time. The result does not determine paid hours, premiums, legal work limits or any contractual entitlement.