Sienna Miller didn't "freak out" as much as she thought she would when she turned 30.

The British actress hit the landmark age in December last year. She worried she wasn't going to deal with it very well, but actually found it quite fun.

"I didn't have the freak-out which I thought I would have. But maybe it's because I'm the youngest of all my friends so that lessened the blow. It's nice to start a new decade. I think being a late something' is worse," she mused.

Sienna found the last few years of her twenties strange. She felt like a lot of things were changing, not all of which she wanted to alter.

The star eventually found a phenomenon which seemed to relate to what she going through.

"Twenty-eight, 29, those are weird ages. Weird sh*t goes on," she told the British edition of Vogue magazine. "There's this theory that Saturn returns to your house between the ages of 27 to 29 and makes things crazy.

"Everyone has a really weird time and it shakes things up, and you learn your lessons. I don't believe it, but at the same time I needed something to cling to so I was like, It's that!'"