User blog comment:IamJakuhoRaikoben/Chapter 468: Memory of the Stars, Review./@comment-4489126-20160110001742/@comment-7418318-20160110201213

But now that you mention the year... how does it make sense that the Dragons all supposedly disappeared in the year 777, if the children were sent through time without their knowledge?

They didn't know how many years the children would be sent into the future, since they had to wait for the right conditions, so just telling the children that they are in 777 when they really are in 377 or somesuch doesn't work.

So are we now supposed to believe that a bunch of children counted the exact days from the moment they were found (and thus learned the current date) backward to the day they woke up alone? Some of those children who were only 5 years old at the time?

Seems pretty weird to me... or rather it seems like Mashima didn't plan to have time-travel originally back when he came up with 7.7.777 and only changed his mind later.