It seems that a PBX I set up to use in Tokyo Japan is experiencing daily interruptions at 16:00 ( Tokyo ) .
If this is the regular time where services are interrupted, I would suggest that perhaps a rolling hour or random hour outage time is more suitable, meanwhile possibly minimizing outages to the most necessary.
In June some maintenances were not to be delayed. But this is done now.
Usually maintenances are scheduled to midnight Central European Time because there is less traffic then. We will announce such maintenances in the forum, if any.