by Saturday – к субботе
when – когда
after – после
before – до, до того как
+ ○ + had + Ved/3f.
I had written a letter by 7 o’clock yesterday.
I had finished my work when you came.
- ○ + had not + Ved/3f.
He had not written a letter by 7 p.m.
I hadn’t finished my work when you came.
? Had + ○ + Ved/3f.
Had you worked by 7 o’clock yesterday? – Yes, I had. / No, I hadn’t.