Find out the Hour of an order' open time?

Hi, Everyone,

How can I use OrderOpentime() to find out the Hour of the order open time? One way I can think is

a=MathMod(OrderOpentime(),60*60*24);
b=MathRound(a,3600);

I think "b" is the Hour of the order open time. Could someone let me know if I am correct or wrong?

Many thanks!

Order_Hour = TimeHour(OrderOpenTime());