Explains the representation of dates in the Gregorian calendar including calendar dates expressed in terms of year, month and day of month; ordinal dates expressed in terms of year and day of year; dates identified by means of year, week numbers and day numbers; time of the day based upon the 24-hour timekeeping system; differences between local time and Coordinated Universal Time, combination of date and time and periods of time, with or without either a start or end date or both. BS AMD 7825 RENUMBERS THIS STANDARD TO BS EN 28601