Optus appears to have accidentally declared itself in favour of adopting daylight saving time in Queensland.
Customers in the state's southeast had their phones automatically switched over to the alternative system on Wednesday morning.
The technical glitch meant many woke an hour earlier than usual - and weren't too happy about the rescheduled wake-up call.
"Thanks for waking me up an hour early!! iPhone system time changed to daylight savings, QLD is cursing you!!" one cranky user tweeted.
Another was similarly unimpressed: "Love waking up at 4:30am for no reason."
The company says handsets were affected by incorrectly set mobile switchers at the company's Brisbane exchanges, and the problem has since been resolved.
"We'd love to say it's a great opportunity to get up early and go for a jog, but it is an inconvenience," a spokesperson told Fairfax radio.
She denied the time swap was a veiled election campaign policy suggestion.
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