Remove seconds

File here...
https://ibb.co/tXjcdh2

By default, the time header displays only hour, minutes and (depending on the locale) the am/pm string.

You can customize the time header HTML using onBeforeTimeHeaderRender event handler:
https://doc.daypilot.org/calendar/time-header-customization/

You might want to check your onBeforeTimeHeaderRender handler to see where the extra string comes from.

Let me know if it didn't help.

Ok.. Found it... It's ok...

But looks there is a bug or something...
To appear good I changed the line
args.header.html = args.header.hours + ":" + args.header.minutes + " *";

to
args.header.html = args.header.hours;
I removed the minutes and they appear anyway.. but good.

I think it was when I switched to:
dp.cellDuration = "15";

Yes, you're right. There seems to be a problem with timeHeaderCellDuration values other than 60.

It should be fixed now in the latest sandbox build (2021.2.5010):
https://javascript.daypilot.org/sandbox/

Ok, Nice.
:)