Tuesday 19 April if renowned tipster Evan Blass (@evleaks) is to be believed: he specified the date in a tweet. He says the date is "nearly a lock" for the launch of the product so you've got a little over six weeks still to wait.
Eagle-eyed observers will have noticed that's the date shown on the official press renders of the device that leaked yesterday, which adds some extra credence to the theory that 19 April is the date HTC has chosen.
Of course it's not official until it's official so don't book the day off work just yet. HTC executives might change their plans and shift the launch date in either direction - but the second half of April would seem to be a good bet.
There have been a slew of leaks about the upcoming device: we're anticipating a 5.15-inch quad HD display, the latest Snapdragon 820 processor and perhaps waterproofing, which would be nice.
HTC has been pretty tight-lipped but did offer up this teaser a couple of weeks ago. Previously 11 April had been earmarked as the launch date, with the device expected to go on sale at some point during May.