Catherine Zeta-Jones hates sharing a birthday with Michael Douglas.

The 'Side Effects' star and her now-spouse were both excited to learn they were born on 25 September when they first met in 1998, but the 'Flatliners' producer admitted the novelty has now worn off.

He said: ''Catherine and I, when we got together, the first night I met her I found out we had the same birthday and that was like, 'Oh man, this is the killer, this seals the deal.' We thought it was so great.

''[But now] she has had it up to here with having the same birthday, she wants her own day now, she's tired of having to share.''

But the 73-year-old actor, who is 25 years older than his wife, insists he is happy for her to take the spotlight on their shared special day.

He added in an interview with 'Extra': ''[Do I give her her own day?] I'll give her anything she wants. I'm crazy about her, but I'm a few years older than her so I'm happy letting it pass.''

Michael and Catherine married in 2000 and went on to have children Dylan, 17, and 14-year-old Carys, and the 'Wall Street' star knew as soon as they met they'd have a future together.

He said: ''The first time I met her, I told her I'd be the father of her children.''

Michael previously admitted he credits his wife for keeping him looking ''sexy'', although he feels like a pre-historic being because he can't get to grips with social media.

Speaking previously about the secret behind looking youthful, he said: ''I'm popping along, a healthy, decent-looking 72. What's the secret to staying sexy at 70? Like your wife and like your work.

''I'm a dinosaur. Thank God for Catherine - one of the huge benefits of having a young, beautiful wife is that she's also very aware of social media and how you get from here to here.''