public static final Period clone(Period period) {
        if (period == null) {
            return null;
        }
        return new Period(period.getFromMs(), period.getToMs());
    }
<p>
Class that represents a period. May have null upper or lower bounds to
indicate before or after a time rather than between 2 times.
</p>
<p>
<p>
The upper bound is not part of the period. E.g. 1/1/2001 to 1/1/2002 does not
include 1/1/2002.
</p>
stroom-util/src/main/java/stroom/util/Period.java