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.
MediaWiki:Apihelp-block-param-expiry
From MarineLives
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.