| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |
Arguments: date-time
Returns the value of the ymd-yd-before-year-0
of
date-time, which must be a date-time
object. The value can be
t
or nil
. t
means the date in date-time is
definitely before the year 0. nil
can mean
that the date is not before the year 0 or that the slot value has not
been calculated and holds its initial value (which is nil
).
The value depends on the value of the ywd-century
(reader date-time-ywd-century: if that value
is positive, the century is not before year 0 and so nil
is the proper value for this function; linewise
the century being negative means t
is the
correct value for this function. If the value of the
ymd-yd-century
is nil
, the
correct value for this function cannot be determined and the initial
value (nil
) is returned.
date-time should be complete (see complete-date-time) before calling this function. Otherwise the slot may be unset even though there is enough date information to set it accurately.
This is not a particular useful value for user code (its is useful for internal code). Users may wish to just look at the century value to determine whether the date is before year 0 or not, if that information is knowable. See also date-time-ymd-yd-before-year-0, which give a different value on January 1, year 0.
See date-time.htm for information on support in Allegro CL for parsing and generating time expressions using the ISO 8601 standard.
Copyright (c) 1998-2016, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 8.1 page.
Created 2010.1.21.
| Allegro CL version 8.2 Unrevised from 8.1 to 8.2. 8.1 version |