I’m currently in the Asia/Nicosia timezone, one which doesn’t appear on Beeminder’s list of timezones, so Beeminder is “helpfully” giving the deadline both in the timezone in my Beeminder settings (Asia/Jerusalem), and also in the timezone my computer is set to (Asia/Nicosia). This is in any case redundant, because both have an offset of UTC+03 at the moment. The timezones switch on and off DST at different times, but that is not relevant here, and you probably could do with avoiding the duplication in cases like this. Because of DST changes it would need to be more complex than just comparing the offsets—but you could calculate the deadline for both timezones and if the result is equal show it just once.
But that aside—in the above tooltip, the result somehow isn’t equal. Is it an off-by-one error, or some sort of rounding thing? Either way, there is something subtly wrong with the calculation here. Even if you’re going to display the same thing twice, at least you should accurately display the correct thing twice.