I am working with a subdaily dataset. My understanding is that the method "date_col_check" checks first whether the "date_col" a Date class is and, if not, then it will convert it to a Date class (see line 539 of the first picture attached), before going to the section referred by @dannyparsons . Then the time information is already removed from the date column before getting to the section referring to the "subdaily_label" (second picture attached)

