Change Time Header Vertical Grid lines style

You can use the following CSS:

.scheduler_default_timeheadercol_inner {
  border-right-width: 4px;
}

Thanks for your reply!

Is it possible to change the style for only specific dates? For instance, I'm considering displaying a thicker border when the date falls on the last day of the month.

Yes. Using the onBeforeTimeHeaderRender event, you can add a custom CSS class to selected time header cells:

onBeforeTimeHeaderRender: args => {
  if (args.header.start.getMonth() !== args.header.end.getMonth()) {
    args.header.cssClass = "last";
  }
}

Your CSS woud look like this:

.scheduler_default_timeheader_cell.last .scheduler_default_timeheader_cell_inner {
  border-right-width: 4px;
}

Hi,

I followed your instructions and it worked perfectly.

Thanks for your help!