Delivery ETAs

A warehouse dispatches each order 6 working hours after it is placed. When does an order placed now leave the building? This guide answers it with add, in Rust, Python and JavaScript.

The scheduleCopy Anchor Link

A warehouse in London is open 08:00–18:00 on weekdays, stops for lunch, and is closed on 25 and 28 December 2026. As rules, in the Europe/London time zone:

• WorkDay: 08:00–18:00, Monday to Friday.
• Break: 12:00–13:00, Monday to Friday.
• Holidays: Friday 25 and Monday 28 December 2026.

Handling takes 6 hours of operating time. One order is placed at 15:00 on Thursday 24 December 2026, London time, and another at 10:00 on Saturday 26 December, when the warehouse is closed.

Find the dispatch timeCopy Anchor Link

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 days = Weekdays::MON_TO_FRI;
    let warehouse = Schedule::builder()
        .time_zone("Europe/London")
        .rule(WorkDay::new(time(8, 0, 0, 0), time(18, 0, 0, 0), days))
        .rule(Break::new(time(12, 0, 0, 0), time(13, 0, 0, 0), days))
        .rule(Holidays::new([date(2026, 12, 25), date(2026, 12, 28)]))
        .build()?;
    let handling = SignedDuration::from_hours(6);

    let placed: Zoned = "2026-12-24T15:00[Europe/London]".parse()?;
    let dispatch = warehouse.add(&placed, handling)?;
    assert_eq!(dispatch.to_string(), "2026-12-29T11:00:00Z");

    let saturday: Zoned = "2026-12-26T10:00[Europe/London]".parse()?;
    let dispatch = warehouse.add(&saturday, handling)?;
    assert_eq!(dispatch.to_string(), "2026-12-29T15:00:00Z");
    Ok(())
}

The resultCopy Anchor Link

The order placed at 15:00 on Thursday 24 December is dispatched at 11:00 on Tuesday 29 December 2026, London time:

The order placed at 10:00 on Saturday 26 December starts counting when the warehouse next opens, at 08:00 on Tuesday 29 December. It uses 08:00–12:00 and 13:00–15:00, and is dispatched at 15:00 that day.

For a delivery leg with different hours, such as a courier that works on Saturdays, build a second schedule for the courier and add its time to the dispatch instant.

Edge casesCopy Anchor Link

• An order that uses up the morning is dispatched at 12:00, when the lunch break starts, not at 13:00: 4 hours from 08:00 on Tuesday end at 12:00 (DESIGN.md A2, Adding time: Where the result lands).
• An order placed during the break starts counting at 13:00: 1 hour from 12:30 ends at 14:00 (DESIGN.md K4).
• Different hours on Saturdays. Add a second WorkDay rule for Saturday with its own hours; working time is the union of all WorkDay rules (Schedules).
• Holidays. Each date in Holidays removes 00:00 to the next 00:00 in the schedule's time zone (Rules: Holidays).
• Daylight saving time (DST). Operating hours are wall-clock times, so 08:00 stays 08:00 London time after the clocks change. An order placed at 15:00 on Friday 27 March 2026 is dispatched at 11:00 on Monday 30 March, London time (BST), which is 10:00 UTC (Time zones and DST).

What 0.1.1 does not do (DESIGN.md: Scope):

• Lead times in business days, such as "delivered in 2 business days". workclock adds working time, not days.
• Different hours on one date, such as closing early on Christmas Eve. Operating hours repeat by weekday, with no per-date overrides. A whole closed day is a holiday.

See alsoCopy Anchor Link

• Adding time: what add and sub return.
• Support SLAs: the same add, with between for the time left.
• Batch operations: dispatch times for many orders in one call.
• Errors: what add raises when there is no working time within the search bound.