when：可接一般现在时/一般过去时,
例如：I was sleeping when my mother came in.（一般过去时）
I am going to be a teacher when I grow up.（一般现在时,主将从现）
until则没有什么明确的要求,一般的结构是not···until,意为“直到……才……”
例如：He didn't stop crying until his mom came.
since：一般加上一个一般过去时的句子
例如：I have been learning English since I was seven years old.