Hi Birdman,
I don't have a good answer for when it was broken but it was a few years ago.
"Zap" timers used to be what we are now calling a "Watch" timer. You just need to look at the EPG code to see the work that went into handling "Zap" timers that had a duration. They had a green lightning bolt icon and coloured the cell green rather than the red as for "Recording" timers. I believe there is a need and place for all three types of timer ("Record", "Watch" and "Zap").
Regards,
Ian.