Here in the UK, national meets are also organised according to age with the youngest often starting at 13-14 but younger swimmers can take part if they meet the required entry time, but the minimum here is 10 years of age. These events are level 1 and faster than level 2 and 3 events.
All national meets are registered with ASA and run with strict discipline. At level 1 meets swimmers can achieve acceptable qualifications times for international meets like Olympic Games, Commonwealth Games, European Championships and others.
The age is also as on the last day of the year in which the competition takes place. Entry packs are published on the Swimming.org website and swimmers usually enter via their club, who send a coach(es) along with the swimmer(s) to the meet.
There are summer and winter meets as published on the Swimmng.org website.
It is every competitive club’s aim to enter as many swimmers as possible in the national competitions, which often produce qualification times for international events.
National events are often life-streamed via You Tube. Links to life events can be found on the British swimming website just prior to the event, they are also highly publiced on social media like Facebook or Twitter.
I strongly advise all aspiring champions to watch these events, there are recordings available on the Youtube Channel.