This is from a native speaker gardener's youtube video where he tells about his roses Roses (see:5:50-5:53)
"This is September now and a lot of my roses are still blooming."
The structure "This is ...." sounded different to me, because when we talk about months, we say "It is (name of the month)" For instance, "It is September, June etc"
So, why does he say "This is September now." instead of "It is September now"?
We usually say It's midday now, not This is midday now - and the same preference applies with It's/This is September now. There's nothing "wrong" with OP's cited usage, though - regardless of whether it's September at time of speaking, or the speaker is providing voiceover / commentary to some footage shot during last September.
Note that this, it, and now all implicitly refer to the current contextually-relevant time, which isn't necessarily the same thing as time of utterance (when the words are spoken).
But - the longer the duration of the time-frame referent, the more likely we are to use this rather than it. So This is 5 past 9 now is incredibly unlikely, but This is the twenty-first century now might actually be more common than It's the twenty-first century now.
