!!! Overview
[{$pagename}] means "Not Before" and is a [Reserved Claim Name] defined in [RFC7519 Section 4.1.5|RFC 7519]

The "[{$pagename}]" (not before) [JSON Web Token Claim] identifies the time before which the [JWT] [MUST NOT] be accepted for processing.  The processing of the "[{$pagename}]" [JSON Web Token Claim] requires that the current date/time __MUST be after or equal to__ the not-before date/time listed in the "[{$pagename}]" claim.  

Implementers MAY provide for some small leeway, usually no more than a few minutes, to account for [clock skew].  Its value [MUST] be a number containing a NumericDate value.  

Use of this claim is __OPTIONAL__.

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]