As others have said, if you're asking about the title specifically, it depends on the company. I was one of those "Senior" developers when I was in my mid twenties at a start-up, whereas for my current company it's actually pretty hard to get the title "Senior Software Development Engineer."
My experience is generally the people I recognize as having deserved the title don't _simply_ just code. Not only do they write code that works and delivers the feature in a timely manner, they make it so the next 3 features to come out in that area can be done quickly by junior developers. Not only do they code, but they make everyone around them better coders. Not only do they code, but they also think strategically about what the team needs to keep going two years from now. Not only do they deliver the project, they get everyone excited about delivering the project.
I once read someone say "there's a difference between having ten years of experience, and having the same year of experience ten times." Time is a factor, but it's also whether you've exposed yourself broadly and deeply to new technologies, approaches and experiences so that when you are in a new situation (technical or otherwise), you have patterns for how to deal (or the self awareness to know that you don't know how to deal). So, part of it is time, but part of it is spending that time wisely.
I'll second this. Titles vary across company size, and even then are different from company to company (e.g a Principal Engineer at Intel would not make PE at Google). I was a Staff Software Engineer at Intel (level above Senior Software Engineer) but now my title is Senior Front End Developer at a startup ;)
My experience is generally the people I recognize as having deserved the title don't _simply_ just code. Not only do they write code that works and delivers the feature in a timely manner, they make it so the next 3 features to come out in that area can be done quickly by junior developers. Not only do they code, but they make everyone around them better coders. Not only do they code, but they also think strategically about what the team needs to keep going two years from now. Not only do they deliver the project, they get everyone excited about delivering the project.
I once read someone say "there's a difference between having ten years of experience, and having the same year of experience ten times." Time is a factor, but it's also whether you've exposed yourself broadly and deeply to new technologies, approaches and experiences so that when you are in a new situation (technical or otherwise), you have patterns for how to deal (or the self awareness to know that you don't know how to deal). So, part of it is time, but part of it is spending that time wisely.