/** Public subscription metadata only. Credentials never enter this contract. */
export interface Subscription {
    plan: string;
    startedAt?: string;
    renewsAt?: string;
    renewsEstimated?: boolean;
    checkedAt?: string;
}
/** Provider identifiers, not arbitrary free text or credentials. */
export declare function planName(value: unknown): string | undefined;
export declare function subscriptionDate(value: unknown): string | undefined;
/** Next anniversary in UTC, always using the original day (Jan 31 -> Feb 28 -> Mar 31). */
export declare function monthlyAnniversary(startedAt: string, now: Date): string | undefined;