Some Apple Watch Series 4 owners in Australia experienced crashes and reboots on Saturday due to a bug that surfaced because of the daylight saving time change (via 9to5Mac).
According to Reddit users hit by the Apple Watch bug, the root of the problem appears to be the Infograph Modular face's Activity complication, which displays a timeline graph with hourly data for the user's Move calories, Exercise minutes, and Stand hours.
When daylight saving time (DST) lops an hour off the typical 24-hour day, the Activity complication is apparently unable to compute the change and draw the timeline graph with only 23 hours, which throws the Apple Watch into an endless reboot loop until the battery runs out.
According to reports, the bug corrected itself when the date rolled over the next day and the normal 24-hour day was reinstated, but some users were able to restore normal function to their watch before then by removing the Infograph Modular watch face via the iOS Watch app.
This isn't the first time Apple has been caught out by daylight saving time changes, but the company has a few weeks yet to fix this latest DST bug before it happens again when Europe and the U.S. change their clocks on October 28 and November 4, respectively.