iat property
The ID token's issued-at time, in seconds since the Unix epoch. That is, the time at which this ID token was issued and should start to be considered valid.
The Firebase SDKs transparently refresh ID tokens every hour, issuing a new
ID token with a new issued-at time. If you want to get the time at which the
user session corresponding to the ID token initially occurred, see the
auth_time
property.
Implementation
int iat;