"至今难以忘怀" 这个表达可以用 "unforgettable to this day" 来表示。它的来源可能来自于古希腊语 "mnēmē"，意思是 "记忆"，在英语中表示为 "memory"。
例句：
The sunset we saw on our honeymoon is unforgettable to this day. (我们在蜜月旅行中看到的日落至今难以忘怀。)
The tragedy of 9/11 is unforgettable to this day. (9/11悲剧至今难以忘怀。)
The taste of my grandma's cooking is unforgettable to this day. (我奶奶做的饭菜的味道至今难以忘怀。)