完全可以.
例如：
1 By yesterday we were ready to set out for Tibet on our first trip there.
2 By the time she was 25,she was a mother of three children.
(注意,这个过去时往往局限于be动词)
但：1 By yesterday,they had left for Tibet on their first trip.
2 By the time she was 25,she had neen married for 6 years and had three children.(注意,这里的have也用一般过去时had,因为have强调的是状态,不是动作.)