Step 9: Define Project Calendars

Calendars define the available working time for activities in the schedule. Getting calendars right is essential — errors here ripple through every date calculation in the program.

Key Rules for Calendars

Calendars must include all non-working time — public holidays, Rostered Days Off (RDOs), weekends, and shutdown periods (e.g. Christmas break).
The number of calendars should be kept to a minimum.
Multiple calendars with different working hours introduce complexity that is often not handled well by scheduling software and can produce unexpected results — including negative float.
When multiple calendars are required, the working hours within each calendar must be the same (e.g. 8 hours per day) to avoid calculation errors.
Consider relevant local Industrial Relations requirements for different trades with respect to working calendars.

Typical Project Calendars

Calendar Type	Work Week	Hours/Day	Non-Working Time
Office-based work Design & Procurement	5-day week	8 hours	Public holidays, 2-week Christmas break
Construction & Installation	5-day or 6-day week	8 hours	Public holidays, RDOs, 2-week Christmas break
Occupations & Closures Curing, rail possessions	7-day week	8 hours	No non-working time

Railway Schedules — Important Note

Detailed railway occupation schedules (hour by hour) should always be maintained in separate schedules outside of the master schedule. Mixing them into the master schedule introduces calendar complexity that can cause significant scheduling errors.

Best practice:

Set up and verify all calendars before entering a single activity. A calendar error discovered late in schedule development can require significant rework to correct across the entire program.

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