没有什么特别的要求，根据用的时候的要表达的意思来决定时态。not ...until直到not...until / till表示“直到……才”not ... until it was too late直到太迟了才要not...till/until直到not..till/until直到not...until = not...befor直到（not ...until)i won't help her until she tells me the truth直到我告诉她真话Not until...did...直到．．．才...
not ...until直到not...until / till表示“直到……才”not ... until it was too late直到太迟了才要not...till/until直到not..till/until直到not...until = not...befor直到（not ...until)i w...
没有固定要求，只要根据意思来就行，例如都表过去的话前后都用一般过去时，或一般现在时也有情况前面用情态动词can could may 等，后面相应的接动词过去时或一般现在时，如We do not understand joy . until we face sorrow .我们不理解快乐，直到面对悲伤；the U.S. economy would ...
