51cd1206_JSON_Web_Token__JWT___Claim_Syntax
[Claim Name] iat [JSON Value Type] number [Claim Semantics] The iat (issued at) claim identifies the time at which the JWT was issued. This claim can be used to determine the age of the token. This claim is OPTIONAL. [Claim Syntax] 
IntDate
I n t D a t e
S t r i n g O r U R I
S t r i n g
JSON Web Token (JWT)
Claim Syntax