Earlier today, it said I could extend the streak again after 11 PM today, I extended it after 11 PM, and then it said I could extend it again after midnight. I took it to mean midnight the next day (25 hours after 11 PM), but now it's just past midnight today (only 1 hour later) and it's already saying "Your streak expires at midnight" again.
(In case it matters, the streak time zone is UTC+0 / UK time)
It resolved itself in October and November last year (when daylight saving ended in the UK and US respectively) and only the timing changed a bit, but maybe that's because it was the "fall back" transition, not "spring forward".