I need to express how an event occurred before-or-at a certain time in the past (non exclusive or, which of the two alternatives is the actual one is left open). For the future I would have used "by", but what about the past? "Until" is for prolonged actions/states only, just like "through", "before" excludes the cutoff moment, and an expression like "by yesterday" seems to me intentionally wrong (both syntactically and semantically).
Or can I actually say something like
Last weekend we went skiing, we had bought the equipment by then.
This is still a special case, as it involves the completion of a "pending" action, not just an event. Does
The concert was held by September.
make sense? What about:
Please provide a list of all his books published before 2000 included.
or is it wrong: are "before" and "included" mutually exclusive?
Are there any other possibilities?