I've noticed a issue using the date picker from the header context menu to navigate through time.
It works fine if you first navigate forward a day, then go back and forth through time, but if the first navigation step is backwards, it seems to often start jumping around multiple days at a time.
Tested on Windows 10, in Firefox 62, Chrome 69, Edge
Steps to reproduce:
1. Open the basic scheduler demo, with a maximised window on a 1920x1080px screen https://www.bryntum.com/examples/scheduler/basic/
2. Right click the header, and press the "<" button to navigate back in time. Mostly it will jump to the 30th December, sometimes the 29th and sometimes the 31st.
3. The unexpected jump size now seems to persist for the lifetime of the picker, whenever navigating forward and back.
Expected outcome:
I would expect the picker to consistently navigate to the 31st December when selecting "<".
Notes:
On a freshly displayed picker, if forward navigation is selected first, it seems to work consistently, one day at a time, in both a forward and backward direction.
Please let me know if there's any more information required, and if you are able to reproduce the problem.
