Hey, man.
Well, in the historical data tester you're working off "virtual time", so in onTick you want to keep track of the ITick.getTime() (inherited from the super interface ITimedData) so you know what "time" it is.
So you need to "schedule" the action and on every tick see whether you are at the right time to do what you need to do, and place the order(s).
But, remember you're working on a "virtual timeline" in the historical tester, so don't use System time in any way for this purpose.
// in onTick
// keep track of time
now = tick.getTime(); // now is defined at global scope as long type
bidPrice = tick getBid();
askPrice = tick.getAsk(); // also defined at global scope as double type
// so on each tick we have the most recent time, and the inside bid/ask prices
You'll need to use Java Calendar classes, I suppose to convert "time in milliseconds since 1970" to a meaningful GMT day time or whatever you need for that...

You could post your code or relevant code fragments and we can certainly give you some tips.
HyperScalper
(If you need help, let me know.)