Here's a cute bit of CSS I was asked for to hide the Saturday and Sunday columns in the new look Calendar widget. It's not really worth a whole tutorial, but it uses nth-child as the individual table cells don't have class names
<style>
div[data-content-uuid="uuid of the widget"] .frogui_components_calendarweekview th:nth-child(7),
div[data-content-uuid="uuid of the widget"] .frogui_components_calendarweekview th:nth-child(8),
div[data-content-uuid="uuid of the widget"] .frogui_components_calendarweekview td:nth-child(7),
div[data-content-uuid="uuid of the widget"] .frogui_components_calendarweekview td:nth-child(8) {
display:none;
}
</style>