Sarah Jessica Parker keeps her 20 year marriage to Matthew Broderick alive by having ''time alone''.

The 'Sex and the City' star has opened about her marriage to her 'Godzilla' actor husband - who she married in 1997 - and admitted her favourite thing to do with her better half is having unplanned ''trips'' without their three children.

Speaking to PEOPLE, Sarah said: ''Oh my god what was it that happened recently. Oh we found ourselves alone, we went away but we didn't realise it, we didn't plan it.

''It just happened because our son was away on a trip and our daughters were otherwise engaged and we ended up alone and it was so amazing and really fun.''

The 'Here and Now' actress - who shares her children James, 16, Marion, 9 and Tabitha, 9, with her Matthew - also added that the couple are always ''happy'' when they spent time together because they schedules are so full.

Sarah added: ''We love going to the theatre, we love eating, we love being with our friends, it's those times are few and far between just because of work and kids schedules, but we're happy we have some.''

The American actress has previously opened about what it was like playing Carrie Bradshaw on her successful 'Sex and the City' HBO TV series, and how the role impacted people's perception of her in real life.

She questioned: ''I'm not sure how seriously women are taken, period. It's not just the characters, it's - how mature are the conversations people want to have with an actor?

''There is an assumption not just about what you endow a male character to possess as a person or personality or traits or shortcomings that we can call and colour all sorts of different ways, but also an assumption about the person playing the part.''