midnight and "12 p.m." for noon. However, the previous 29th edition of the U.S. Government Printing Office Style Manual (2000), in section 12.9, recommended the opposite. There is no further record documenting this change. The US National Institute of Standards and Technology (NIST) recommends avoiding confusion altogether by using "11:59 pm" or "12:01 am" and the intended date instead of "midnight" or "12:00 am". There are several common approaches to identifying and distinguishing the precise start and end of any given day. Use of a 24-hour clock can remove ambiguity. The "midnight" term can be avoided altogether if the end of day is noted as 24:00 and the beginning of day as 00:00. While both notations refer to the same moment in time, the choice of notation allows its association with the previous night or with the following morning. "Midnight" can be augmented with additional disambiguating information. A day and time of day may be explicitly identified together, for example "midnight Saturday night." Alternatively, midnight as the division between days may be highlighted by identifying the pair of days so divided: "midnight Saturday/Sunday" or "midnight December 14/15." The approach recommended by the NIST ("12:01 a.m." or "11:59 p.m." instead of midnight) can be particularly helpful when any ambiguity can have serious consequences, such as with contracts and other legal instruments. A clear convention may be legally defined or culturally promulgated. For example, the Hebrew calendar associates the start of a new day with sundown and midnight being a relative hour falling six hours after sundown. Similarly, in traditional Arabic time at sunset, which marked the start of each new day, clocks were reset to 12:00. As noted above, however, such conventions or definitions may not be uniformly observed. The International Standards Organization (ISO) in specification ISO 8601 states: "midnight may only be referred to as '00:00', corresponding to the beginning of a calendar day." The AP Stylebook assigns "midnight" to the day that is ending, not the day beginning. References External links National Institute of Standards and Technology Parts of a day Night