code: private void writeTimecolumn(LongColumnVector col, String columnType,int cIdx,
                                 int rowNumber, ParseWriter dout) {
      boolean timestamp = columnType.equals("timestamp");
      long [] oneColumn = col.vector;
      if(col.isRepeating) {
        long val = timestamp ? oneColumn[0] / 1000000 : correctTimeStamp(oneColumn[0]);
        for (int rowIndex = 0; rowIndex < rowNumber; rowIndex++)
          dout.addNumCol(cIdx, val, 0);
      } else if(col.noNulls) {
        for (int rowIndex = 0; rowIndex < rowNumber; rowIndex++)
          dout.addNumCol(cIdx, timestamp ? oneColumn[rowIndex] / 1000000 : correctTimeStamp(oneColumn[rowIndex]), 0);
      } else {
        boolean[] isNull = col.isNull;
        for (int rowIndex = 0; rowIndex < rowNumber; rowIndex++) {
          if (isNull[rowIndex])
            dout.addInvalidCol(cIdx);
          else
            dout.addNumCol(cIdx, timestamp ? oneColumn[rowIndex] / 1000000 : correctTimeStamp(oneColumn[rowIndex]), 0);
        }
      }
    }
docs: This method writes one column of H2O frame for column type timestamp.  This is just a long that
  records the number of seconds since Jan 1, 2015.
  
  @param col
  @param cIdx
  @param rowNumber
  @param dout