It's possible that there is no translation to your language which specifically has that meaning, so that context is required to clarify it. I think this is the case with Slovak for instance:
Keby tu bola Anna, bola by vedela by čo robiť.
This has two meanings: "If Anna were here, she would have known what to do." as well as "If Anna had been here, she would have known what to do". The distinction, if any is necessary, is clear from the context. We can add additional words to indicate the time that we mean meaning over the "were" meaning:
Keby tu bola Anna, vtedy keď sa to stalo, bola by vedela čo robiť. [If Anna had been here, at the time when it happened, she would have known what to do.]
Keby tu dnes bola Anna, bola by vedela čo robiť. [If Anna were here today, she would have known what to do.]
In general, if some grammatical tense distinction is missing in a language, you can make up for it with explicit indications of time or some additional context (which is the medicine that cures all sorts of semantic ailments).
Continuing with your examples:
Note that "be changed" is awkward, especially in this last one. One problem is that whenFor one thing, the cause of the change is not clear, we normally do not use: the change is caused by the Earth stopping. The passive voice "to be changed" is used when the agent of change is unknown, butor we tendwish to just useconceal it. In this case, the reflexive formnatural way to express it is from the point of "to change":view that is to say, something can just changechanges are taking place globally, spontaneouslyby themselves, rather than "be changed" (by some unnamed agency)in response to the Earth stopping: in other words, the reflexive form of "to change".
If the Earth stops, everything will change in the world. [ Much better! ]Things will change, by themselves, but in response to or as a result of the stopping.]
This may be the key to unraveling these present tense subjunctives combined with past clauses: invertnegate them.
For instance "If Anna were here, she would have known what to do.". What What is the negative way of saying "If Anna were here?" PerhapsTry:
If Anna hadn't taken a daytoday off, she would have (been here and) known what to do.
No.
The last example, in various tenses:
