Quick plugin I banged out per a thread request. Didn't too a ton of testing, so if you have issues let me know.

Give users timekick.exempt to make them exempt from the checks. In the kick and uptime message configuration you can use %time% to display raw time (# of seconds), %timelong% to display like "2 hours, 5 minutes, 1 second" or %timeshort% to display like 00:02:05:01.

Commands

/TK SETMSG message
timekick.setmsg
Sets the message displayed to users when they are kicked

/TK SETDELAY #
timekick.setdelay
Sets the amount of time (in seconds) the server will be unavailable post start/reload

TK ENABLE
timekick.enable
Enables functionality

/TK DISABLE
timekick.disable
Disables functionality

/TK RELOAD
timekick.reload
Reloads configuration from disk

/TK UPTIME
timekick.uptime
Display time the server has been up

/TK STATUS
timekick.status
Displays plugin configuration/status

Only tested under 1.18 but it should work on older versions too. If you try and it pukes, send me the stack trace (the big error that will appear in the server log)