JWT & Authentication· Updated 2026-08-30· 3 min read

How JWT Expiration Works: Understanding exp, iat, and nbf

JWT tokens rely on Unix Epoch timestamps (in seconds) to manage session validity without maintaining database session lookups. This reference details how time-based claims interact.

Table: Standard RFC 7519 time-based claims.
Claim	Name	RFC Meaning	Validation Rule
exp	Expiration Time	Time on or after which the token must not be accepted	Reject if CurrentTime >= exp
iat	Issued At	Time at which the JWT was generated	Must not be in the future (subject to clock skew)
nbf	Not Before	Time before which the JWT must not be accepted	Reject if CurrentTime < nbf

Interactive Tool

Timestamp Explorer

Convert JWT Epoch Timestamps

Convert 10-digit JWT Unix timestamps into UTC and local date formats.

Preset Payload

1788134400

JWT & Authentication· Updated 2026-08-30· 3 min read

How JWT Expiration Works: Understanding exp, iat, and nbf

JWT tokens rely on Unix Epoch timestamps (in seconds) to manage session validity without maintaining database session lookups. This reference details how time-based claims interact.

Table: Standard RFC 7519 time-based claims.
Claim	Name	RFC Meaning	Validation Rule
exp	Expiration Time	Time on or after which the token must not be accepted	Reject if CurrentTime >= exp
iat	Issued At	Time at which the JWT was generated	Must not be in the future (subject to clock skew)
nbf	Not Before	Time before which the JWT must not be accepted	Reject if CurrentTime < nbf

Interactive Tool

Timestamp Explorer

Convert JWT Epoch Timestamps

Convert 10-digit JWT Unix timestamps into UTC and local date formats.

Preset Payload

1788134400