Well, not the first, but the first for the PC.
the program started off for the Commodore 64, some time around 2007, it really did not do anything except repeat back what you put into it, it made no calculations at all.
it was also ported to dos, which was quite easy since it really did nothing but repeat back everything you said, Commodore Basic is 90% compatible with MS-QuickBasic. I did not even bother to fix the capitalization reversal.
Version 2.0 was quite a bit more advanced, you input the day and month of the show and the current day and month and it would tell you how many months and days it is until the show, it often reported negative numbers.
it was ported to DOS as well, which was a bit more involved. I fixed the reverse-capitalization and made the colors work right, notice it's still made for a 40 column display.
Version 2.0 was also ported to Windows, there was a 16-bit version made in Visual Basic 1 and a 32-bit version done in Visual Basic 2008, both of those were eventually lost. Their functionality was basically the same as their DOS and C64 counterparts.
After I lost those versions, development sort of halted, that is until I made the single-purpose Stay Sweet Fest countdown clock. I built it all new and used some of it's code to make Show Countdown 1.0 for Windows (Concert Countdown 3.0)
You no longer have to put the current time into it, it also calculates hours and minutes! it still has a problem with negative numbers.
I am considering porting it to OS/2 and Windows 3.x and maybe even DOS.
Download both Commodore 64 versions here (Concert_Countdown-C64.zip, 4kb)
Download both DOS versions here (Concert_Countdown-DOS.zip, 51KB)
Download the Windows version here (SC_INSTALL.EXE, 88kb)