We'll look into that. Possibly StartWeek does not affect the day functions and Sunday is always included. We`ll provide a solution.

Ok, I learned that StartWeek has indeed no effect here, and Sunday is included. Since this is undesired, we will change this in the next update, but until then you can skip Sunday in this way:

int Offs = ifelse(dow() == MONDAY,3,1);
Lowx=dayLow(UTC,Offs);
Highx=dayHigh(UTC,Offs);

Thank you very much for this workaround! it would take me a lot of time to figure out in this way... but still there is something strange look to screenshot:



Same script with your workaround with dates :
StartDate = 20170505;
EndDate = 20170518;

Looks ok to me. Don't forget: It is not the high/low of the day, it is the high/low within the defined market hours.

You can check the prices in the log when you set Verbose to 2. You see then the OHLC prices of any bar and can compare. If you find something wrong, just post the part of the log here.

Ah of course, beginner mistakes ... thank you many times!