Date is represented by integer serial values where the base
   date is Dec. 30, 1899 (which equals 0).
Time is represented as a fraction of a 24 hour period, such
   that 12 Midnight = 0 and 12 Noon equals 0.5.
Date and time may be represented in a single real number,
   where the integer portion equals the date and the
   fractional part the time of day.
Date/time arithmetic is fully supported; however, it's up to
   you to decide what operations are meaningful. That is,
   subtracting one date value from another gives the number
   of days between them and is certainly valid, but I'm not
   sure what it would mean to, say, square a date value.
In order to display these numbers in a recognizable format,
   a special date/time format is supported. This is
   described at the end of this section.
DATE(year,month,day): Returns a serial number representing
   the desired date. Year should be year after 1900.

YEAR(expr): Returns the year of the serial date value.

MONTH(expr): Returns the month of the serial date value.

DAY(expr): Returns the day of the month of the serial date.

WEEKDAY(expr): Returns the day of the week of the serial
   date value. The range is 1-7, where Sunday = 1.

DAYSMONTH(month,year): Returns the number of days in the
   calendar month. Year is years A.D.

ISLEAP(year): Returns TRUE (1) if the year is a leap year
   and FALSE (0) if it isn't. Year is years A.D.

TIME(hour,minute,second): Returns a fraction representing
   desired time. TIME follows the military convention, where
   hours range from 0-23.

HOUR(expr): Returns the hour, which falls in the range 0-23.

MINUTE(expr): Returns the minute (0-59).

SECOND(expr): Returns the seconds (0-59).

NOW(): Returns a value representing the current date and
   time, as given by the ST's system clock.
Opus provides 9 default date/time formats; six user-defined
formats are available, and the formats are constructed from
the symbols below.

   yyyy: full year
     yy: last two digits of year
   mmmm: full month name
    mmm: abbreviated month name
     mm: month number with leading zero if necessary
      m: month number
   dddd: full day name
    ddd: abbreviated day name
     dd: day number with leading zero
      d: day number

     hh: hour with leading zero
      h: hour
     ii: minutes with leading zero
      i: minutes
     ss: seconds with leading zero
      s: seconds
  AM/PM, am/pm, A/P, and a/p.

Any symbols not included above are taken literally, making
possible formats like "mmmm d, yyyy h:ii:ss." However, you
can't use "Day = dddd," because the y would be interpreted
as a year format symbol. If you need to create such formats,
you will have to define a number format string and assign
this format, in addition to the date format, to the cells
of interest.
