Doesn't this mean 'this time'? If not, how do you simply say 'this time'? Conversely if it does how do you say 'at this time'?
In Greek, the concept of "time when" is usually expressed with accusative. This does not require the preposition. Θα συναντηθούμε την Δευτέρα, we will meet ON ΜΟΝDAY. However, η Δευτέρα, is simply "Monday," being nominative. You cannot translate it as "on Monday." Likewise, αυτή η περίοδος does not make sense as "at this time." Nominative case has a very strict use in Greek. It is basically used for the subject of a sentence, or a noun in apposition with the subject, or a predicate nominative (usually following a linking verb). It would logically have to be αυτήν την περίοδο, accusative, to express "at this time."
But D I write "αυτός ο άντρας" or "ο άντρας" when translating from English " The man" and both are marked correct? But you can't do the reverse, is that it?
Uh, no. In the alternative that you just mentioned, nominative and accusative are mixed up. One can either say "Αυτή η περίοδος", οr "Αυτή την περίοδο". Not all translations are word-for-word.
@Atheia @Joanna206443 @Walt1965 @Kalikur
This sentence is a bit... awkward. Normally, the Greek sentence should have been in accusative instead of nominative, since there is at in the Engish sentence. However, I do feel like this time would translate to αυτήν τη φορά in Greek, with the meaning of this time, and not some other time, and not to αυτήν την περίοδο, which refers to a period of time. Again, the Greek sentence and its translation is a bit weird to begin with, so I understand the confusion. :/