public static long parseDate(byte[] data) {
        return parseDate(data, 0, data.length);
    }
The number of days from year zero to year 1970.
There are five 400 year cycles from year zero to 2000.
There are 7 leap years from 1970 to 2000.
indexr-common/src/main/java/io/indexr/util/DateTimeUtil.java