@manton, good morning. I believe the “x new today” message at the top of the Mentions page is not using local timezones. I always have more mentions than the ones that are actually from “today” and the counter goes down as the hours pass on my timezone (UTC 0).
@vladcampos It's actually the last 24 hours. "Today" is sort of a lie, but I found that it's more useful that way.