it was 和it is +before这两个的时态要注意吗

it was 和it is +before这两个的时态要注意吗 it is ...since it was...before 一定是过去式吗? It is/has been…since… It was/will be…before… 这两个句 It was…before…后面用什么时态呢? it was(is) ...that+什么时态 it will be…before和 it was …before的区别 it is the first time和it was the first time后面接的时态各是什么? it is not the same as it was before It was...before 句型 It is（was） the first time后的从句只能用完成时态吗? It won't be long before和It is before long that的区别 It was different from before 中before 是代词吗