What Time I Should Trade in Forex?

The best forex time to trade is depend on your currency that you want to be traded, and also how long is your time in trading forex.
Because forex is 24 hour non stop trading I am sure you won't have time to trade all day long, you must chooce your trading session.
In forex there are four session.
1. New zealand-australia at 04.00-12.00
2. Singapore at 9.00-15.00
3. Europe 14.00-21.00
4. Usa at 20.00-04.00

if you trade in forex asia currency like Yen Japan or Australian Dollar,its much better if you choose Asia session or Australia session.
And you may choose Europe or USA session for major currency/forex.

And don't forget to see what news is released at that time/session forex trading.