couldn't I also use ..εποχη instead of περιοδος ???
Yes, it's added. Thanks.
Such an ending for a feminine noun?
Yes. Words in -ος can be masculine, feminine, or neuter.
οδός and all of its compounds (e.g. περίοδος, μέθοδος, σύνοδος, ...) are feminine.
very very helpful comment mizinamo