The term "day period" refers to a specific time frame within a 24-hour day. It can be used to describe a portion or segment of the day, usually measured in hours. For example, if someone says they worked for an eight hour day period, it means that they were working for a continuous block of time that spanned from morning until evening. The term "day period" is also commonly used when referring to specific times of day such as morning, afternoon or night.