Time intervals are consistent within a given file.
The first line is a header that contains the monitoring station ID code , the year in which the data were obtained, and a series of element numbers that describe the data in each column. Since each data value is followed by a data quality flag , element numbers are followed by a zero, which acts as a placeholder so element numbers line up with appropriate data columns. Data begins on the second line. The first number is the day of the year. The next column indicates the ending time of the measurement in military time format.