DATE([option][,date[,option]])

When used with zero or one arguments, the DATE function returns the
current date in a user-defined format.  When used with two or three
arguments, it converts the date given in the second parameter from
one format to another.

The format in which the date will be output is given by the first
parameter, whose first letter must match that of one of the options
listed below.  If the parameter is omitted then 'N' is assumed.

Base    - the theoretical number of days in the common era (i.e. since
          1/1/1 AD).  On 1/1/1900 the result would be 693595.
Century - the number of days so far since the zero year of the most
          recent century (so on 1/1/1900 or 1/1/2000 the result would be
          1).  This option is deprecated and was not adopted by ANSI; use
          the Base option instead.
Days    - the number of days so far in this year (so on 12 Jan 1986 the
          result would be 12).
European- the date in the format dd/mm/yy.
Julian  - the date in the format yyddd (where ddd is as in "Days" above).
          This option is deprecated and was not adopted by ANSI.
Month   - the full name of the current month, e.g. August.
Normal  - the date in the format dd Mmm yyyy, e.g. 27 Aug 1982 (with no
          leading zero).
Ordered - the date in the format yy/mm/dd.
Standard- the date in the format yyyymmdd.
USA     - the date in the format mm/dd/yy.
Weekday - the full name of the current day, e.g. Tuesday.

If a date is given in the second parameter, the third parameter must
state what format it is in (if the third parameter is omitted then 'N'
is assumed).  The possible values for the third parameter are the same
as listed above, with the exception that options 'W' and 'M' are not
allowed.  If the input date has a two-digit year then the century is
chosen so as to make the year no more than 49 years before or 50 years
after the current year.

On the first call to DATE or TIME in an expression, a time stamp is
made which is then used for all calls to these functions within that
expression.  Hence if multiple calls to these functions are made within
a single expression, they are guaranteed to be consistent with each
other.

BUG: The DATE function only works within the limits defined for Unix
     dates (usually approximately 1902-2037), and in any case the
     DATE('C') function only works between 1900 and 2099.  Using 'C' for
     the input format may occasionally result in the wrong century being
     chosen if the given date is very close to 50 years from this
     year.    
BUG: The DATE function is slightly lenient in what it accepts as a valid
     date from the second parameter.  For instance, "30 Feb 1997" would
     be accepted as if it said "2 Mar 1997".