The term DAY UNIT is composed of two words, HOUR being the first one. HOUR is a 4-letter word that refers to a unit of time equal to 60 minutes or 1/24 of a DAY. It is commonly used to measure the duration of events and activities. The second word, DAY, is a unit of time equal to 24 hours or 1/7 of a week. It is used to measure the length of time between two points in time. Together, DAY UNIT is a unit of time equal to 24 hours or 1 DAY.