private static String zeroPad(final int amount, final String in) {
        final int left = amount - in.length();
        final StringBuilder out = new StringBuilder();
        for (int i = 0; i < left; i++) {
            out.append("0");
        }
        out.append(in);
        return out.toString();
    }
@return The {@link Period} of this {@link TimePeriod} in terms of the passed time zone.
stroom-util/src/main/java/stroom/util/time/TimePeriod.java