Jump to today button Label
This is a i18n option! i18n options can not be set directly on a per-instance basis, you must include the "override" directive, and properly camel case the new name - (i.e. overrideTodayButtonLabel). For more information, please take a look at the Localizing Datebox section.
This began life as a CalBox only option, and still retains that name. However, it is used in all modes now.