A quick test of Vivaldi with some of those shows it nowhere near as strict as your Firefox is. Amusingly new Date("2025-07-12 12:30:45 BST") is an invali

A quick test of Vivaldi with some of those shows it nowhere near as strict as your Firefox is. Amusingly new Date("2025-07-12 12:30:45 BST") is an invalid date, whereas all three of new Date("2025-07-12 12:30:45 GMT") new Date("2025-07-12 12:30:45 UTC") new Date("2025-07-12 12:30:45 Z") are valid but in British Summer Time.