How to restore "all day" option for events in iCloud calendar?

On Imac desktop (High Sierra v. 10.13.1), the all day option for events in iCloud Calendar has disappeared. It did not happen in connection with an upgrade.

I don't use the calendar as a standalone, only through iCloud.

I can still use the option on the iPhone 6S, so the current workaround is to enter events on iCloud Calendar on the iMac, and then edit them to all day on the phone.

Is there a better solution out there?

Thanks.