These rules are included in the HVA Rules at section C.11 under "Time restricted venues".
The rules clarify that any venue time restriction must be communicated by the Home Captain to both the Away Captain and the Referee at the start of the match, with the situation under which the match will end clearly stated. Perhaps it might be a good idea to write it on the score sheet before the match starts to avoid any confusion!
It's then up to the Referee to end the match as and when agreed. If this isn't clearly communicated and agreed before the match, the home team risks forfeiting all incomplete points.
The examples given in the rules are the match ending at a specific time or "when the caretaker arrives". It's probably also good form to state if the venue doesn't have any time restrictions for those lucky enough to have that flexibility.
This all supposes the match started on time. If either team delays the start and the match cannot be completed within the agreed time, then different rules come in to force and the offenders risk forfeiting any unfinished matches.
Of course, if you know you're restricted for time, starting as soon as everybody ready is not a bad idea either!