Yup, but when the age has been (let's say) 23 for an year and becomes 13, the software should smell a mistake.
Of course I have no idea about the actual UI. It's a bad idea to ask for the age because it doesn't update after the birthday. A birth date is much better but it's also personal data and maybe not necessary. If all a site wants to know is if you're 18, just ask it and store a boolean. If you suddenly declare that you're not >= 18 anymore, especially after using the site for a while, smell a misclick on a checkbox, ask for confirmation and explain what's going to happen.
It’s an engineering cost decision. I imagine they get single figure numbers of people making this change each year. The cost of having a developer design and implement a system to catch it, reject the change but save it in a state where it can be applied later, and automatically open either a support ticket or have an automated resolution system is far too high. Much easer to just lock the account and ask the customer to get in touch.
(Assuming there is a save button on the screen and it’s not an auto save on an input change, in which case yes it needs a confirmation dialog)
The software does smell something is off. Typically the policy in this case is that legal told them to deny then access, because they don't want to deal with the legal hassle of serving someone who just told you themselves that they're not 13 yet. (Lawyers are often unreasonably risk-averse.)
>Yup, but when the age has been (let's say) 23 for an year and becomes 13, the software should smell a mistake.
some years ago the Danish electrical company Dong (wonderful name they've since changed for 'reasons') sent me a message - give us a meter reading for your house or we will send someone around to do it and it will cost you some money, so I figured fine I don't have to do anything they do it for me for money!
next year, the same thing.
third year, the same thing. In Christmas of the third year when I was in Berlin I got an email from Dong, you owe us 15 thousand dollars (approx. translating from dkk in head), then later same day you owe us 18 thousand dollars, and finally next morning you owe us 20 thousand dollars.
So naturally I called them up and said I sure would like to know what you all are thinking (which was a lie, I didn't really want to know but I figured I better find out anyhow)
So they said they had sent someone by to read our meter and we had used more electricity and they wanted their money or they were turning it off. So I said you think I used 20 thousand extra dollars in a year?
No, the meter hasn't been read for three years and this is your fault because when we send you a notice to go read the meter you have a moral obligation to do that.
I asked what about their moral obligation to go read the meter when they said they would (which point they did not understand) but anyway since I was supposed to pay 3 thousand dollars a year (which is somewhat high for a Danish family of 3) and paid that it seemed highly unlikely that I had managed to use over two times more than I was estimated to use per year without an increase in population of the house.
It took a lot of arguing to convince them that somehow there was something fishy in the situation and they might have made a mistake, before they would put it to off closing the electricity and do an investigation.
Some months of investigation later, which involved me going to take pictures of my meter etc., it turned out they had read the wrong meter.
tldr: even obvious discrepancies that systems could easily be set to catch will not be caught and you will have to do the work to fix the problems of the organizations providing you services.
Of course I have no idea about the actual UI. It's a bad idea to ask for the age because it doesn't update after the birthday. A birth date is much better but it's also personal data and maybe not necessary. If all a site wants to know is if you're 18, just ask it and store a boolean. If you suddenly declare that you're not >= 18 anymore, especially after using the site for a while, smell a misclick on a checkbox, ask for confirmation and explain what's going to happen.