18.104.22.168 Extended Years
The ECMAScript 3rd Edition Specification [ECMA-262-1999] requires the ability to specify 6-digit years (extended years). This amounts to approximately 285,616 years, either forward or backward, from 01 January, 1970 UTC. To represent years before 0 or after 9999, [ISO-8601] permits the expansion of the year representation, but only by prior agreement between the sender and the receiver. In the simplified ECMAScript format, such an expanded year representation shall have 2 extra year digits and is always prefixed with a plus (+) or minus (–) sign. The year 0 is considered positive and therefore is prefixed with a plus (+) sign.