Scheduler seems to incorrectly render events which are “out of boundaries” when first_hour is used (maybe it affects last_hour as well - I have not tested that).
Here is an example: https://snippet.dhtmlx.com/0eskodhd
The first hour is set to 8am. Notice the overlapping (the events are set to .5 opacity in the CSS)
The red and the blue events are from 7am till 8am and thus out of bounds and should not be rendered.
The yellow event is overlapping them both and is the only one correctly rendered.
It looks like setting 0 seconds on an event forces it to render. This you can test with the red event. I assume it is happening with the json (blue) event as well when you convert it from string.
An override/workaround would be REALLY appreciated! This is a blocking issue for me because it will be used in different timezones and thus this can occur any time. Thanks.