〜ことになっている
N3
V（辞書形 / ナイ形）+ ことになっている
「〜ことになっている」表示某种事情已经被决定或者约定好了，通常是由外部的规定、约定、习惯等决定的，而不是由说话者自己决定的。
可以理解为某种事情已经被规定成这样了，是一种客观存在的状态。
比如，公司规定每周五要开会，你可以说:每周五开会已经成为惯例了。
再比如，某个城市规定晚上十点后不能大声喧哗，你可以说:在这个城市，晚上十点后已经被规定为安静时间了。
总之，这个语法用来表达一种已经被决定或者约定好的状态，是一种客观存在的规定。
The grammar pattern "~ことになっている" is used to express that something has been decided, arranged, or is expected to happen in a certain way.
It implies that there is a certain rule, agreement, or circumstance that has led to the current situation.
For example, if you say "明日は雨が降ることになっている" (Ashita wa ame ga furu koto ni natte iru), it means "It has been decided that it will rain tomorrow" or "It is expected to rain tomorrow", indicating that there is a plan or expectation for rain based on certain circumstances.
～という決まりである / 〜することが決まっている
已经约定好每周五开会。
It has been decided to have a meeting every Friday.
在这个城镇，晚上十点后已经被规定为安静时间了。
In this town, it has been decided to keep quiet after 10 p.m.
新员工已经被规定每天提交报告。
New employees are required to submit reports daily.
在这所学校，已经被规定穿校服。
It is required to wear a uniform at this school.
在这家酒店，已经被规定退房时间是11点。
Check-out time at this hotel is set at 11 a.m.
她已经约定每天慢跑。
She is scheduled to go jogging every day.
在这家店，已经被规定禁止使用信用卡。
It is prohibited to use credit cards at this store.
他已经被规定每周三做志愿活动。
He is scheduled to do volunteer work every Wednesday.
在这个国家，已经被规定酒后驾车将受到严厉处罚。
Drunk driving is strictly punished in this country.
在这家电影院，已经被规定禁止使用手机。
The use of mobile phones is prohibited at this movie theater.