MediaWiki:Apihelp-block-param-expiry
From SaveTheWorld - a project of The Partnership Machine, Inc. (Sponsor: Family Music Center)
Expiry time. May be relative (e.g. 5 months or 2 weeks) or absolute (e.g. 2014-09-18T12:34:56Z). If set to infinite, indefinite, or never, the block will never expire.