When do you see/perceive-that a Dev transit from junior to senior?

I'm an undergrad, working, by now, for 9 months in companies meanwhile studying, I have found that I didn't really had any difficult time dealing with the requirements/specs in the working environment, I always found myself being able to adapt to the problem and deal with it, and by this way of doing I can hardly see myself as a junior. What do you think about? (Excuse me for any mistake, I'm drink)

Probably something to do with age and years employed.

I haven't seen a concrete formula though.

Some might say, It's when you stop giving a rats ass about being up-to-date and just does your thing as you've "always" done em.

I think it differs from company to company, but basically I can share some thoughts as I was there as well:
- company that only looks at age and 'how many days you are working here' are most of the time shitty ones. They promote employees for basically 'spending time on sitting on chair', saw that in two companies so far, where guys with 8-year exp just had to be promoted, even tho some didnt had skills to fill up Senior Role
- so called Seniors, that shows up as persons that has 'everything figured out' are usually using same argument: We always did it that way, so you will do it that way. Thats the most dangerous sentence you can hear. It shows thats someone is close minded and not ready for change person.
Finally: ability to adapt, mentoring, solid work, setting up quality standards in team, cold blood when prod blows up, ability to take a lead in team on technical decisions and even working with client, all this for me defines a Senior. Its a full package dev that will ekevate team