Generic Function | Package: util.date-time | ToC | DocOverview | CGDoc | RelNotes | FAQ | Index | PermutedIndex
| Allegro CL version 10.1 Unrevised from 10.0 to 10.1. 10.0 version

## date-time-ymd-yd-before-year-0

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 `ymd-yd-century` (reader date-time-ymd-yd-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-ywd-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) 1998-2022, Franz Inc. Lafayette, CA., USA. All rights reserved.
This page was not revised from the 10.0 page.
Created 2019.8.20.

|  | ToC | DocOverview | CGDoc | RelNotes | FAQ | Index | PermutedIndex
| Allegro CL version 10.1 Unrevised from 10.0 to 10.1. 10.0 version