Add 8 working hours.
Land on Wednesday at 09:30.

Same answer in Rust, Python and JavaScript

use jiff::civil::{date, time};
use jiff::{SignedDuration, Zoned};
use workclock::{Break, Holidays, Schedule, Weekdays, WorkDay};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let support = Schedule::builder()
        .time_zone("Europe/London")
        .rule(WorkDay::new(time(9, 0, 0, 0), time(17, 0, 0, 0), Weekdays::MON_TO_FRI))
        .rule(Break::new(time(12, 0, 0, 0), time(13, 0, 0, 0), Weekdays::MON_TO_FRI))
        .rule(Holidays::new([date(2026, 12, 25), date(2026, 12, 28)]))
        .build()?;

    let opened: Zoned = "2026-12-24T16:30[Europe/London]".parse()?;
    let due = support.add(&opened, SignedDuration::from_hours(8))?;
    assert_eq!(due.to_string(), "2026-12-30T09:30:00Z");

    let now: Zoned = "2026-12-29T11:00[Europe/London]".parse()?;
    assert_eq!(support.between(&opened, &now), SignedDuration::from_mins(150));
    Ok(())
}

How you can check it

• Every rule and edge case is specified with an example and an ID.

  DESIGN.md

• The Rust, Python and JavaScript test suites all run the same file of examples, so the bindings cannot disagree on them.

  tests/fixtures/design_examples.json

• Each binding is compared with a brute-force oracle on random schedules: proptest (Rust), Hypothesis (Python), fast-check (JavaScript).

  oracle_properties.rs, test_properties.py, properties.test.ts

• workclock.compat is tested against businesstimedelta 1.0.1 where 1.0.1 is correct, and against the oracle everywhere.

  tests/python/test_differential.py

• businesstimedelta’s own test suite runs against workclock.compat in CI.

  tests/python/upstream

• Each upstream bug it fixes has a test: issues 8, 9, 10 and 12, and overnight shifts.

  tests/python/upstream_issues

• CI fails if line coverage of the Rust crate drops below 90%.

  ci.yml, job coverage

• Tested on Linux, macOS and Windows; Python 3.9 and 3.15; Node.js 22, 24 and 26; Rust 1.85 checked separately.

  ci.yml, jobs test, python-test, wasm, msrv

• Benchmarks compare every binding with businesstimedelta 1.0.1, with medians, p95s, date and machine.

  RESULTS.md

• The npm package is published with provenance, so npm shows which workflow run built it.

  release.yml, job npm

• PyPI packages are published from GitHub Actions with trusted publishing, without a stored token.

  release.yml, job pypi; Release Process

• Every GitHub Action is pinned to a commit SHA.

  ADR 0002

• MIT licence. Rust 1.85+, CPython 3.9+, Node.js 22+.

  LICENSE, README requirements

What it is for

• Support-ticket SLAs

  When is a ticket due, and how much of its SLA has elapsed?

  add, between

• Payroll and overtime

  How many hours of a shift fell inside contracted time?

  between

• Staff rosters, including overnight shifts

  When does the next shift start and end?

  next_period / nextPeriod

• Delivery ETAs that only count operating hours

  When does a parcel arrive?

  add