\section{Glossary}\begin{description}\item [date] \label{glos:date} A date is used to specify an instant of time at the Greenwich meridian.  It consistsof year, month, day of month and time of day components.\item [time] \label{glos:time} A time is used to specify an interval of time.               \item [calendar day] \label{glos:calendarday} The day number in the calendar year. January 1 is calendar day 1. Calendar day expressed in a floating point format is used to express the day number plus the time of day at Greenwich. For example, assuming a Gregorian calendar: \begin{tabular}{ll}{\bf date}              & {\bf calendar day} \\\hline 10 January 2000, 6Z     & 10.25 \\31 December 2000, 18Z   & 366.75 \end{tabular}\item [no-leap calendar] \label{glos:noleap} Every year uses the same months and days per month as in a non-leap year of a Gregorian calendar.\end{description}