If you are thinking of arbing that one source for instant risk-free profit, go ahead and do it... if you can.
With the sole, well known exception of Oanda, there are no retail forex brokers open for trading on weekends, to the best of my knowledge. (I'd love to be proven wrong on this.) Whatever quotes you are seeing elsewhere, away from 238.05/25 currently (bid = Friday close), are just for giggles; they are not executable. What, no free lunch?! surprise.