"12 hours" refers to a time duration that equals half a day. It is commonly used in various contexts, such as scheduling, work shifts, and travel. For example, a typical work shift might last for 12 hours, allowing employees to complete their tasks efficiently. In terms of timekeeping, 12 hours can be represented in two formats: the 12-hour clock and the 24-hour clock. In the 12-hour format, the time is divided into two cycles of 12, with designations of AM for morning hours and PM for evening hours. This system is widely used in countries like the United States.