Maintaing HUB world files:

To ensure that the universe age is updated properly, you must only
perform warm boots or keep from deleting files in /save during cold
boots.  The universe age is only for informational purposes and is
shown to administrators by the "uptime" command.  (It can be calculated
by:

 ( age of "root" )  +  (current time) - (boot time aka uptime)