User blog comment:Ugo2001/Potential Plot Hole?/@comment-34109241-20171227192843

I don't think Oda ever gave a time frame for how long they were sailing back then. These days he will make notes that the Strawhats have been sailing for. For example after Dressrosa the Strawhats sailed for 1 week along with Barto before they arrived at Zou(Chapter 802). And after Zou the Strawhats sailed for another week, with the manga noting "several days later" on 2 different occassions(824 and 825) before they arrived into Big Mom's territory. But back then in the early days of the series I don't think he was concerned about the time frame, so he probably didn't even put much thought into it. So I think people may have just assumed it was a few days when actually it could have been weeks sailing between islands just like it is now.