This International Standard specifies the representation of dates in the Gregorian calendar and times and representations of periods of tirne. It includes a) calendar dates expressed in terms of year, month and day of the month; b) ordinal dates expressed in terms of year and day of the year; c) week dates expressed in terms of year, week number and day of the week; d) tirne of the day based upon the 24-hourtimekeeping system; e) differences betvveen local tirne and Coordinated Universal Time (UTC); f) combination of date and tirne; g) time-intervals; h) recurring time-intervals. This International Standard is applicable vvhenever dates and times are included in information interchange. This International Standard does not cover dates and times where vvords are used in the representation and dates and times where characters are not used in the representation. This International Standard considers the leap seconds that are occasionally inserted at the end of a calendar month to maintain astronomic precision of the calendar day. This International Standard does not assign any particular meaning or interpretation to any data element that uses representations in accordance with this International Standard. Such meaning will be determined by the context of the application.