There is an interesting discussion concerning the words “last” and “next”.
Suppose it were Autumn now.
When someone said “last summer,”
would you think it refers to the one in the same year or the previous year?
Similarly, would “next winter” be the one in the same year or the next year?
According to some dictionaries, “last” refers to something that occurred most recently, and the “next” one is something coming immediately after the present one.
For this reason, some people insist that both should refer to the ones in the same year; while, others say that they don’t use those words that way.
Take another example of days of the week.
When someone says “last Monday” on Wednesday, I presume most people would take it for “Monday last week”, not for the one in the same week since we just say “on Monday” for it. It seems, however, that some people take it for the one in the same week for the same reason we saw above.
As you see, the words “last” and “next” are sometimes very ambiguous.
Maybe in those cases we should specify the year or the date to avoid misunderstanding.