Perth is the one capital where "business hours" on the other side of the country are already afternoon tea. A service rostered to Sydney's clock is thin by your lunchtime and gone before your last job; a diary that assumes +10 offers your 9am at 11am Perth time. Perth businesses have been quietly working around both for years.
Giday runs on Perth's clock, and it answers around the clock with no after-hours surcharge — so the call at 6pm Perth time is just a call, not an "after-hours" one priced off someone else's day.