Knowledge Base
The Project Work Calendar
Working days, not calendar days
An activity's duration counts the days a project actually works. Ten days on a Mon-Fri project spans two full weeks; the same ten days on a project that works Saturdays finishes a day and a half earlier. Everything that turns a duration into dates walks this calendar: the Schedule action, the Start, Finish and Duration fields on an activity as you type them, and the Gantt.
Projects that existed before the work calendar did work seven days a week, where a working day and a calendar day are identical, so no stored date or duration moved when it arrived. New projects start on a Mon-Fri week.
The working week
Working days sits on the project's Settings page (open a project, then its actions menu), as a row of weekday toggles. At least one day has to stay on.
Changing it moves nothing by itself. Dates are only ever rewritten by Schedule, which says how many activities a run would move before it writes anything (see "Scheduling Work in the Programme Register"), so widening or narrowing the week is a decision you get to look at before committing to it. Until then the programme keeps the dates it has, and its durations start meaning something the dates no longer show.
Anyone who can edit the project can change its working week.
Days off
There are two lists of days off, and a project observes both.
Organisation holidays are entered once and inherited by every project in the organisation, which is what stops the same public holidays being retyped project by project. They are managed from the Manage organization menu in the top navigation, and mirrored on the Team page. Only organisation admins can change them, since a day added here re-times every programme in the organisation the next time each one is scheduled. A year's worth can be pasted straight in or read from a two-column file of date and label, with dates written as YYYY-MM-DD (a bare 03/04/2026 is a different day either side of the Pacific).
Project holidays sit on the project's own Settings page, beside the working days, and are added on top of the inherited list. A site shutdown or a local show day belongs here. Anyone who can edit the project can add one.
Either list is a date and a label per entry, and a date can only appear once in a list, so re-entering a year you already have updates the labels rather than doubling the days up. There is no holiday feed and no country calendar: the days off are the ones you enter.
A project cannot un-observe an organisation holiday
Project holidays only ever add days off. Nothing removes an inherited one.
The organisation's list is the organisation's decision, and a project that genuinely works through one of those days says so by widening its working week, which is visible on the settings page rather than buried as a silent per-project exception.
What the calendar changes
Schedule starts a successor on the next working day after its predecessor finishes, and never leaves an activity starting or finishing on a day off.
A programme rate is quoted per working day, so a duration derived from one lands on the same calendar the dates are built from. A rate quoted per week is divided by this project's working week, so 60 m² per week is 12 m² a day on a five-day project and 10 on a six-day one (see "The Rate Library").
A baseline taken before a calendar change stays comparable against dates scheduled after it, because variance is measured on dates rather than on durations (see "Baselines and Schedule Variance").
Nothing else changes. This says what a day means, not what the scheduler works out: there is still no float and no critical path.