From what I understand, "Legendary" is awarded if you get at least 200 rep in a day 150 times, but that 200 rep is allowed to include the +15 from answer acceptance and bounty rewards.
If this is the case, then the "next badge" tracker in the Activity page is showing the wrong kind of progress under "today rep". It shows only rep from upvotes, not from accepts. As an example, yesterday I earned 240 rep on StackOverflow, 180 from upvotes and 60 from accepts. The legendary counter incremented today, as did the "earned at least 200 reputation" counter in
/reputation. But, at the end of the day, the "next badge" tracker only showed "180/200 today's rep".
Additionally, as a minor issue, the day counter doesn't quite match
/reputation: the day counter says 142 days for me, but
/reputation says 144 days.
EDIT: Seems like Epic was reworded to say "daily reputation" too. So now I'm confused - are both Epic and Legendary for getting 200 rep via upvotes in a day, or are both for getting at least 200 rep from any source? I have only hit 200 rep via upvotes on 128 days, which would make the counter grossly incorrect in that case.