Add Business Hours to a Date

Answers "if I start now and burn N working hours, when am I done?" — useful for SLA targets, ticket due dates, or planning effort that has to fit between 09:00 and 17:00 with weekends and holidays subtracted. Configurable work window, working-day toggles (Mon–Fri default, change for Sun-start cultures or 6-day weeks), and a free-form holiday list. The breakdown lists each working day touched and how many hours were consumed there.

The breakdown is worth reading rather than skipping to the answer, because it shows where the hours actually went. A start time outside the work window is pushed to the opening of the next working period before any hours are counted, so a ticket raised at 18:00 on Friday consumes its first hour on Monday morning and the elapsed calendar time bears no relation to the working hours spent. That gap is precisely what an SLA is meant to express and precisely what people are surprised by.

The work window is treated as continuous. A lunch break is not modelled, so a 09:00 to 17:00 day counts as eight hours rather than seven, and a team that stops for an hour should configure the window to match, or accept that every multi-day estimate drifts by an hour per day.

Everything runs in your device's time zone. An SLA agreed with a customer in another country is measured against their working day, not yours, and a calculation done here from a different zone lands on the wrong hours entirely. Daylight saving is the same trap in miniature: the day a clock shifts has 23 or 25 hours in it, but the working window is defined by wall-clock times and still counts eight.

Holidays are pasted rather than looked up, for the same reason they always are: national holidays differ, some follow a lunar calendar, and a company's own closures are not published anywhere.