Calendar Alerts A Week Early

Calendar alerts are occurring a week early, even though they are not set with a one-week alert.

For example, I created a calendar event to cancel a subscription on December 26, 2021. The only alert is set to "At time of event."

The calendar alert popped up on my Apple Watch 7 (version 8.3 (19S55)).

In previous instances over the past several weeks, the too-early alerts have popped up on my iPhone 13 Pro Max (version 15.1.1) as well.

Why is this happening?