The documentation (§10.3. Using the Scene index) recommends this way to make a scene last 3 turns:
Train Stop ends when the time since Train Stop began is 3 minutes.
But if the scene began less than four minutes before midnight, this means it will never end!
time of day variable in Inform 7 is the current game time in minutes since midnight. At midnight, it is 0. So if the Train Stop scene occurs a minute before midnight, it happens at time of day 1439. When
time of day passes 1439, it goes back to 0, assuming the standard pace of 1 minute per turn. Then time since 1439 (when Train Stop began) will be -1439 minutes. The next turn it will be -1438 minutes. One minute before the next midnight, the time since Train Stop began will be 0. It will never be 3.
I’ll open an issue about this at the unofficial bug tracker as well.
EDIT: I suppose the simplest fix is to write
Train Stop ends when the time since Train Stop began is 3 minutes or the time since Train Stop began is -1438 minutes.