Quick Take:

Some Californians received a test of the earthquake early-warning system seven hours before the appointed time, waking them at 3:19 a.m. Thursday. The warning was supposed to be scheduled for 10:19 a.m. Thursday.

Some Californians appear to have received a test of the earthquake early-warning system seven hours before the appointed time, jolting them awake at 3:19 a.m. Thursday instead of sounding at the more civilized hour of 10:19.

Groggy recipients reached for their phones as they heard the MyShake app say aloud: “This is a test of the earthquake early warning system. This is only a test.”

The error appears to have occurred at least in part because the warning was scheduled for 10:19 a.m. UTC — Coordinated Universal Time, also known as Greenwich Mean Time — rather than Pacific Daylight Time.

“Very uncool to get ‘a test of the earthquake warning system’ at 3:19AM. Now my dog thinks I should definitely get up,” @witchy_aunt posted on Twitter.

At the overnight shift at KTVU-TV, the Fox affiliate in Oakland, a number of phones in the newsroom flashed and buzzed with the alert on the predawn shift.

“Looks like someone screwed up,” Andy Clausen, a producer at the station, posted on Twitter.

It was unclear how many people received the errant MyShake test warning.

The test warning comes after many in Northern California received an actual alert a day earlier, on Wednesday. A magnitude 4.2 earthquake hit the southwest Sacramento County area, close to Contra Costa, Solano and San Joaquin counties, at 9:29 a.m. Wednesday.

Towns near the epicenter, a rural area in the Sacramento-San Joaquin Rivers Delta, reported only light shaking from the temblor. A number of people across the San Francisco Bay Area and Sacramento region also reported weak shaking.

Earthquake scientists have noted previously that the early-warning system, when activated, will sometimes issue warnings for quakes that are not felt by the people who receive them.

There have been a number of times recently when the earthquake early-warning system has worked with impressive results. About a year ago, many in the San Francisco Bay Area received several seconds’ warning before they felt shaking from a magnitude 5.1 earthquake that struck under the mountains east of San Jose.

This story originally appeared in Los Angeles Times.

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