public String getOffsetString(final UTCDate value) {
        final String tz = parseTimeZone(value);
        String offset = tz.replaceAll("GMT", "");
        offset = offset.replaceAll(":", "");
        if (offset.length() == 0) {
            offset = "+0000";
        }
        return offset;
    }
Shifts the currently specified date by the given number of months. The day
of the month will be pinned to the original value as far as possible.

@param deltaMonths - number of months to be added to the current date
stroom-core-client-widget/src/main/java/stroom/widget/datepicker/client/DateTimeModel.java