export declare class AssertableDate extends Date {
    isBefore(other: Date): boolean;
    isInThePast(): boolean;
    isAfter(other: Date): boolean;
    isInTheFuture(): boolean;
    plusMillis(milliseconds: number): AssertableDate;
    minusMillis(milliseconds: number): AssertableDate;
    millisFromNow(): number;
}