MT4 trading hours for most instruments are from 21:05h GMT* (00:05h on Monday server time) on Sunday to 20:55h GMT* (23:55h server time) on Friday, with a daily break between 20:55h GMT till 21:05h GMT.
JForex standard trading hours for most instruments are from 21:00h GMT* (00:00h Monday server time) on Sunday to 21:00h GMT* (23:00h server time) on Friday.
For detailed information on trading hours per instrument, please see HERE