/**
 * The `exp` claim of a JWT, in unix seconds, or undefined for a token that is opaque or unreadable.
 *
 * Decoded, never verified: a browser holds no signing secret, and a signature it cannot check tells it nothing. This
 * is only ever used to skip asking a question the token already answers — "has this lapsed?" — and never to grant
 * anything. A forged `exp` buys an attacker one refused request from the server, which is the only opinion that counts.
 */
export declare const tokenExpiresAt: (token?: string | null) => number | undefined;
/** Unix seconds, the unit every expiry in this package is stated in — `Date.now()` is the odd one out. */
export declare const nowInSeconds: () => number;
export declare const toSeconds: (expiry?: number | null) => number | undefined;