This is why I ignored you. Dude comes on my fucking thread to spew nonsense and doesn't even provide a link or source and yet tells me to go buy the manga. Fuck off my thread.
Of course you should buy the manga. That's part of being a decent participant although like I said, scans are easy.
It's also easy to guess this is a joke alt since somehow you ignore me but are aware of my responses. But it would be funnier if you were some weirdo obsessed with poring over hundreds of chapters to bitch about some perceived inconsistencies. 300 chapters to make some arbitrary connection. Constantly getting angry over some shit you're voluntarily reading for free.
Roger asks a broad question and gets a simple answer. Sharley is asked a question that narrows down to within a year, and she answers while she's bleeding on the floor.
As readers we would understand a few things. Obviously the true answer is just a few months from when Fishman Island took place. But we also understand that if Sharley said a specific date outside of that arc, it would have removed a degree of tension from what was happening at that moment. While simultaneously not meaning anything to us, because serial stories don't account for time so strictly. Hawkins prediction early in Wano was extremely vague, but asking Sharley and getting a response of "next month" would mean nothing as a reader. "Possibly now" holds weight, and having gone through that arc without the prophecy coming true means that Luffy can potentially return at any time to fulfill it.