A calendar date is a reference to a particular day, represented within a calendar system, enabling a specific day to be unambiguously identified. Simple math can be performed between dates; commonly, the number of days between two dates may be calculated, e.g., "25 August 2026" is ten days after "15 August 2026". The date of a particular event depends on the time zone used to record it. For example, the air attack on Pearl Harbor that began at 7:48 a.m. local Hawaiian time (HST) on 7 December 1941 is recorded equally as having happened on 8 December at 3:18 a.m. Japan Standard Time (JST).