representation_of_Gregorian_date_and_UTC

representation_of_Gregorian_date_and_UTC_time

A <representation_of_Gregorian_date_and_UTC_time> is a <class_of_information_representation> whose members are representations of time using the UTC system of time identification as specified in ISO 8601:2000 together with the Gregorian system for representing dates.
All times shall be represented using UTC representation of time. Dates shall follow the Gregorian calendar.
NOTE Coordinated Universal Time (UTC) is the basis for legal time worldwide and follows TAI (see below) exactly except for an integral number of seconds, presently 32. These leap seconds are inserted on the advice of the International Earth Rotation Service (IERS) (http://hpiers.obspm.fr) to ensure that, on average over the years, the Sun is overhead within 0.9 seconds of 12:00:00 UTC on the meridian of Greenwich. UTC is thus the modern successor of Greenwich Mean Time, GMT, which was used when the unit of time was the mean solar day. International Atomic Time (TAI) is calculated by the BIPM from the readings of more than 200 atomic clocks located in metrology institutes and observatories in more than 30 countries around the world. TAI is made available every month in the BIPM Circular T (ftp://62.161.69.5/pub/tai/publication). It is estimated that TAI does not lose or gain with respect to an imaginary perfect clock by more than about one tenth of a microsecond (0.0000001 second) per year.

EXPRESS specification:

ENTITY representation_of_Gregorian_date_and_UTC_time

SUBTYPE OF (

class_of_information_representation);

year

INTEGER;

month

OPTIONAL INTEGER;

day

OPTIONAL INTEGER;

hour

OPTIONAL INTEGER;

minute

OPTIONAL INTEGER;

second

OPTIONAL REAL;

WHERE

valid_month	:	{1<= month <= 12};
valid_day	:	{1<= day <= 31};
valid_hour	:	{0<= hour <= 23};
valid_minute	:	{0<= minute <= 59};
valid_second	:	{0.0 <= second < 61.0};

END_ENTITY;

Attribute definitions:

year	:	The year as defined in the Gregorian calendar. The year shall be completely and explicitly specified using as many digits as necessary to unambiguously convey the century and year within the century. Truncated year numbers shall not be used.
month	:	The position of the specified month in a year as defined in ISO 8601:2000, 5.2.1; the value shall be between 1 and 12 inclusive.
day	:	The value of day as defined in ISO 8601:2000, 5.2.1; the value shall be between 1 and 31 inclusive.
hour	:	the hour element of a specified time on a 24 hour clock; the value shall be an integer between 0 and 23 inclusive. Midnight shall be represented by the value zero. NOTE Although ISO 8601 allows two representations for midnight, 0000 and 2400, this part of ISO 15926 restricts the representation to 0000.
minute	:	the minute element of a specified time; the value shall be between 0 and 59 inclusive.
second	:	the second element of a specified time; the value shall be from 0.0 and up to but not including 61.0. NOTE A value of 61.0 allows for leap seconds. The mean solar time is determined by the rotation of the earth. Leap seconds are added or subtracted as required, usually in the middle or at the end of a year, and ensure that the legal time does not differ from the non-uniform mean solar time by more than one second, in spite of the variations of the earth's rotation.

Formal Propositions:

valid_month	:	month shall be between 1 and 12 inclusive
valid_day	:	day shall be between 1 and 31 inclusive
valid_hour	:	hour shall be between 0 and 23 inclusive
valid_minute	:	minute shall be between 0 and 59 inclusive
valid_second	:	second shall be from 0.0 and up to but not including 61.0