If either localtime_r() or mktime() return a error result, don't use use the
non-sensical time.
Nelgin has reported that under some conditions, he sees:
Your time has been reduced due to an upcoming event on Wed Dec 31 1969 18:00:00
when using Ctrl-T (time info hot key).
I don't have an explanation for this, but if either of those function calls
failed in getnextevent(), something like this could happen. <shrug>