IClock

interface IUtcOnlyClock<TDate> {
  utcNow(): TDate;
}

interface ILocalOnlyClock<TDate> {
  localNow(): TDate;
  withTimezone(timezone: TimezoneDefinition): this;
  hostTimezone(): TimezoneDefinition;
  get timezone(): TimezoneDefinition;
}

interface IClock<TDate> extends IUtcOnlyClock<TDate>, ILocalOnlyClock<TDate> {}

• utcNow() — the current instant, in UTC, as the plugin's TDate. Always available.
• localNow() — the current instant, rendered in the clock's configured local timezone. Only on timezone-aware plugins (IClock, not IUtcOnlyClock) — see Timezones & Local Time. If no timezone was ever configured, assumes "Etc/UTC".
• withTimezone(tz) — reconfigures the local timezone on an already-built clock, returning this for chaining.
• hostTimezone() — the IANA timezone of the current host machine, regardless of what the clock is configured to.
• .timezone — the currently configured local timezone (a plain TimezoneDefinition, i.e. a string).

IManualClock

interface IManualClock<TDate> extends IClock<TDate>, IAdvanceable<IManualClock<TDate>> {}

interface IAdvanceOptions {
  years?: number;
  months?: number;
  days?: number;
  hours?: number;
  minutes?: number;
  seconds?: number;
  milliseconds?: number;
}

interface IAdvanceable<TSelf> {
  advance(advanceOptions: IAdvanceOptions): TSelf;
}

Only on a manual clock (see Manual Clock). advance() moves the clock's time forward (or backward, with negative values); when more than one field is set, they apply to the current time in the fixed order years → months → days → hours → minutes → seconds → milliseconds, since combining calendar-variable fields with others can otherwise give a different result depending on the order. Any setTimeout/setInterval callback that becomes due as a result runs synchronously, in-line, before advance() returns — see Deterministic Scheduler.