Jamie Lee Curtis "doesn't understand" how she has been married for so long.
The 66-year-old actress tied the knot with Christopher Guest on December 18, 1984 but as they approach their ruby anniversary, she admitted that she has no idea how much time has passed since then.
Speaking on 'The Today Show', she said: "40 years of marriage. 40 years married to Christopher next Wednesday. But I'm the most immature guest you've ever had, so how is it possible that I have been married for 40 years? I don't understand that!"
The 'Freaky Friday' star - who has Ruby, 25, and Annie, 34, with Christopher - was mostly known for her role as Laurie Stode in the 'Halloween' franchise when she married Christopher, whilst he had emerged in the starring role of the mockumentary 'This Is Spinal Tap' but she explained that because they have both branched out into other roles within showbusiness, they have been able to "grow" together as a couple.
She said: "Chris wasn't a director when I met him, I wasn't a writer. Chris wasn't a producer when I met him, I wasn't a producer when he married me. We have grown into these new jobs that we have done. He still makes me laugh more than any human being and I'm sure that there is something about me that he likes. I don't know what it is, but I am sure that there's something!"
The 'My Girl' actress explained that she initially had "big plans" to celebrate the milestone with her husband but in the end, nothing has come to fruition and they are just going to embrace being able to be together at the same time.
She said: "I have big plans. We also live in a house that is 100 years old. I had big plans, I was like 'Honey, our house is 100 years old, we're 40, let's have a big party in our house.' Gone, nothing! We are gonna celebrate just by being in the same city at the same time together."