It used to be called the "sandbox" ... where new sites go before they get to start ranking well. Google has done away with that [supposedly].
Basically, Google factors in the age of a domain when it tries to determine how credible it is. There are so many fly-by-night companies nowadays, and domain names can be bought for a buck and change. Essentially, Google gives more weight to the domains that have been around since the 90s or early 2000s.
One site isn't going to rank over another because it's a few months older ... but a decade older, just maybe.
I also with the same point of view that there is no penalization. I have ranked a lot of new domain. These days I am working on a UK Magazines related website. It is just 7 months old and Now it is at no 6 position against "UK Magazines" keyword and top ten for some other keywords in the google UK. But one thing is sure google certainly consider domain age while ranking (means the expiry time of domain).
Old domain is a very good idea to rank higher faster but you won't get penalize for having a brand new domain. Just advertise a lot and have unique back links and keep your website current and fresh content. update your website as much as you can.
My personal experience says, that if you are doing white SEO, write unique interesting content, domain age is not so important. I used to raise my website into top10 in 3 month. I don't believe in sandbox.