Kristen Bell and Dax Shepard celebrate never-ending birthdays.

When talk show host Jimmy Kimmel wished her a belated happy birthday on Tuesday, she said: "Well, you're in luck because it's still my birthday.

"In our household we have a rule that Dax made up, where it's your birthday until you decide it's not your birthday anymore. It's really good.

"Last year, it went well into September. He just made it up one day. He was like, 'No, it can be your birthday until you decide it's not your birthday anymore.' I was like, 'Perfect!' He doesn't go as long as I do. He usually goes, like, two weeks."

Kristen relishes her limitless birthday as it means she can make all the decisions for their entire household.

She explained: "With a limitless birthday you just get to make all the decisions, so you get to choose what we watch on TV, you get to choose if we go to the park or not, you get to choose what we eat for dinner--if we stay in, if we go out. You get to make all the decisions that basically affect everybody."

However, the 'Frozen' star admitted the unusual rule doesn't include the couple's daughters, Lincoln, three, and 19-month-old Delta.

She said:"You have to be over 18 for this rule to apply."

A few months ago, Dax appeared on Jimmy's show and admitted he had had a vasectomy without first discussing it with his wife, but Kristen insisted she wasn't annoyed at him for sharing the story as they have such an open household and rarely get embarrassed.

She said: "We're people like that like embarrassment. I think it makes everything a little lighter and brighter when you can be cool about your embarrassing stories. There are very few things I think that I'd ever say, 'Oh, please don't tell that story.'

"Someone in the household is always nude, or the kids are always nude, or he's running from room to room as he's changing...It doesn't really matter."