大家好,小跳来为大家解答以上的问题。since的用法时态口诀，since的用法这个很多人还不知道,现在让我们一起来看看吧！
1、since的四种用法 1) since +过去一个时间点 (如具体的年、月、日期、钟点、1980, last month, half past six)。
2、 I have been here since 1989. 2) since +一段时间+ ago I have been here since five months ago. 3) since +从句 Great changes have taken place since you left. Considerable time has elapsed since we have been here. 4) It is +一段时间+ since从句 It is two years since I became a postgraduate student.。
本文到此分享完毕，希望对大家有所帮助。