Editing ISO 8601 (section)

===Years===
{| class="infobox" style="text-align:center; width:23em"
| YYYY
|-
| ±<u>Y</u>YYYY
|}
ISO&nbsp;8601 prescribes, as a minimum, a four-digit year [YYYY] to avoid the [[year 2000 problem]]. It therefore represents years from 0000 to 9999, year 0000 being equal to 1 [[Anno Domini|BC]] and all others [[AD]], similar to [[astronomical year numbering]]. However, years before 1583 (the first full year following the introduction of the [[Gregorian calendar]]) are not automatically allowed by the standard. Instead, the standard states that "values in the range [0000] through [1582] shall only be used by mutual agreement of the partners in information interchange".<ref>{{Cite book |title=ISO 8601:2004(E) |date=2004-12-01 |publisher=[[International Organization for Standardization|ISO]] |at=section 4.1.2.1 General}}</ref>

To represent years before [[Year zero|0000]] or after [[Year 10,000 problem|9999]], the standard also permits the expansion of the year representation but only by prior agreement between the sender and the receiver.<ref>{{Cite book |title=ISO 8601:2004(E) |date=2004-12-01 |publisher=[[International Organization for Standardization|ISO]] |quote=3.5 Expansion ... By mutual agreement of the partners in information interchange, it is permitted to expand the component identifying the calendar year, which is otherwise limited to four digits. This enables reference to dates and times in calendar years outside the range supported by complete representations, i.e. before the start of the year [0000] or after the end of the year [9999].}}</ref> An expanded year representation [±<u>Y</u>YYYY] must have an agreed-upon number of extra year digits beyond the four-digit minimum, and it must be prefixed with a + or − sign<ref>ISO 8601:2004 sections 3.4.2, 4.1.2.4</ref> instead of the more common [[Anno Domini|AD/BC]] (or [[Common Era|CE/BCE]]) notation; by convention 1 BC is labelled [[year zero|+0000]], 2 BC is labeled −0001, and so on.<ref>For example, see Annex B.1.1 of the standard.</ref>