"A full and warm day."
Translation:O zi plină și caldă.
Seems that it would not be proper to do so... I've only seen ziua used in the greeting 'Bună ziua!', whereas when describing a type of day with a particular adjective, it is 'zi', such as in 'O zi frumoasă' (a beautiful day) or 'O zi lungă' (a long day).