private static Integer parseMonthToTransformMonth(String monthStr) {
    String[] parts = monthStr.split("-", -1);
    Preconditions.checkState(parts.length == 2);
    int year = Integer.parseInt(parts[0]);
    int month = Integer.parseInt(parts[1]);
    int years = year - ICEBERG_EPOCH_YEAR;
    int months = month - ICEBERG_EPOCH_MONTH;
    return years * 12 + months;
  }
In the partition path months are represented as year-month, e.g. 2021-01. We
need to convert it to a single integer which represents the months from '1970-01'.
iceberg/iceberg-handler/src/main/java/org/apache/iceberg/mr/hive/HiveIcebergFilterFactory.java