How can we obtain the GMT time of a datetime variable?

 
When it's not sunday or a holiday that the broker clock is equal to timecurrent() we can obtain the GMT time of a datetime variable t:

t - ( timecurrent() - timeGMT() )

But is there a function that give us the value of timecurrent() - timeGMT() when a broker time isn't changing?
 
Try TimeTradeServer() instead of TimeCurrent(). TimeTradeServer is always ticking.