Measurement of execution time of method returns wrong value

[petrlicman]

🐛 Describe the bug
Current implementation of time measurement in several methods is wrong, it uses milisecond component and everything else is ignored, it return wrong values always less than 1s.

To Reproduce
Find code there this is used:
DateTime start = DateTime.Now;
double elapsed = DateTime.Now.Subtract(start).Milliseconds / 1000.0;

Expected behavior
Implement some global helper for this, because it is used on several places. Use Stopwatch (prefered) or Ticks at least instead of DateTime.Now because clock can be changed by user, NTP sync ....