Here’s when millions of UK phones will sound an emergency test alarm

Most U.K. cell phones will sound an alarm for 10 seconds later this month as the government tests a new emergency alert system.

A siren will go off at 3 p.m. local time on April 23 and last approximately 10 seconds on all 4G and 5G mobile phones.

The system is designed to broadcast urgent messages to areas that are in danger, for example if there is severe flooding or a wildfire. Similar systems are already in place in other countries, including the U.S., Canada and Japan.

The time and date were chosen in an attempt to avoid disrupting major events such as the London Marathon and large soccer matches, the government said.

The system will only be used “very rarely,” the government said, and alerts will only be sent out when there is an “immediate risk” to people’s lives.

“It could be the sound that saves your life,” Oliver Dowden, a British government minister said in a press release.