public MutableClock adjust(TemporalAdjuster adjuster) {
    instant = ZonedDateTime.now(this).with(adjuster).toInstant();
    return this;
  }
Applies the given {@link TemporalAdjuster} to the internal time.

@param adjuster the adjuster to use,
@return this
spock-core/src/main/java/spock/util/time/MutableClock.java