The 24-hour clock is the convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today,See the Common Locale Data Repository for detailed data about the preferred date and time notations used across the world, as well the locale settings of major computer operating systems, and the article Date and time notation by country.