If you drive across the vast expanse of Australia's Nullarbor Plain along the Eyre Highway from Perth to Adelaide, you encounter a temporal twilight zone. Between Caiguna and the South Australian border, roughly 200 people live by an offset called Australian Central Western Standard Time (ACWST: UTC+08:45).
An Unofficial, Grassroots Time Zone
Under the statutes of the Western Australian Parliament, the entire state is legally mandated to observe Western Standard Time (AWST: UTC+08:00). Meanwhile, South Australia observes Australian Central Standard Time (ACST: UTC+09:30).
When traveling east across the state border, drivers traditionally had to adjust their clocks by 1.5 hours (or 2.5 hours during South Australian Daylight Saving Time). For the isolated communities living along the far southeastern rim of Western Australia—including Eucla, Border Village, Cocklebiddy, Madura, and Mundrabilla—neither Perth's clock nor Adelaide's clock matched local daylight.
Perth sits 1,400 km to the west, meaning if Eucla used Perth time, the sun would rise as early as 4:30 AM in summer and set at 5:30 PM. To remedy this, the roadhouse operators and local pastoralists informally split the 1.5-hour difference down the middle, adopting UTC+08:45 (exactly 45 minutes ahead of Perth and 45 minutes behind Adelaide).
Official Status vs. Practical Reality
Although never codified in the Western Australia Standard Time Act of 2005, the state government recognizes ACWST for local police stations and school operations. Even telecommunications providers in the area calibrate cell towers to UTC+8:45.
Roadhouses Along the 350-Kilometer Corridor
The ACWST zone stretches along the Eyre Highway from Caiguna (near the famous 90-Mile Straight road sign) eastwards to Border Village just inside the South Australian border line:
- Caiguna: Home of the John Eyre Motel and the start of the 146.6 km straight road stretch.
- Cocklebiddy: Famous cave diving capital of the Nullarbor.
- Madura Pass: Overlooking the scenic Roe Plains escarpment.
- Mundrabilla: Remote cattle station and essential fueling post.
- Eucla: Historical telegraph station community nestled against coastal sand dunes.
For technical specifications and timezone database documentation on this zone, consult the IANA tzdb database entry for Australia/Eucla.