Question about the Time in the Data files

Why does the time for January 1st start at 2 am?

Also, is the time of day for the data in AM/PM local or UTC and is day light savings accounted for?

The time convention in SAM depends on the time convention in the weather file. For the TMY files prepared by NREL and available from the National Solar Radiation Database (NSRDB), the first row of data in the file is for the hour ending at 1 am on January 1st, local time. Those weather files do not account for daylight savings. You can read more about the time convention in the TMY files in the TMY user manuals available on the NSRDB website .

Best regards,
Paul.