code: public static Date randomDateBefore(Date before) {
      checkArgument(before != null, "Before must be non-null");
      Instant instant = randomInstantBefore(before.toInstant());
      return Date.from(instant);
    }
docs: Returns a random {@link Date} that is before the given {@link Date}.
  
  @param before the value that returned {@link Date} must be before
  @return the random {@link Date}
  @throws IllegalArgumentException if before is null or if before is equal to or before {@link
  RandomDateUtils#MIN_INSTANT}