No problem, you need two S3K devices, two clock controlled AC outlets, and the problem is solved

This is the "brute force" approach, but it is fastest and may be easiest to implement (also, may be cheapest, depending on the value of your time)
You can also run a script in windows and restore two separate S3K configuration at preset times (but you'll need a windows computer up 24/7), or, if you are really patient, you can hook up a modem to S3K phone port, and change the dial plan using DTMF codes via a script in something like Procomm for Windows (much more painful, specially if you never used any modem scripting language before)..... You can have your device to reload a config file over the LAN from a local tftp server once every hour, and you can switch config files on the server as you see fit (cron job unde *nix or whatever scheduler you want to use under w32).
None of the current devices I know of can deal with two or more dial plans, depending on the time (although all have access to time servers over the net).