An overview of the time classes (arcpy.sa)

Time classes are used to specify the time configuration for calculating solar radiation. There are four types of time classes to specify a period of time within a single day, for multiple days in a year, for special days (solstice and equinox), and for a whole year.

TimeMultipleDays	Defines a multiple day time period within a given year to perform solar calculations. A year, start day, and end day are specified.
TimeSpecialDays	Defines the summer solstice/equinox/winter solstice days as the time period to perform solar caclulations.
TimeWholeYear	Defines a year, using monthly intervals, to perform solar caclulations.
TimeWithinDay	Defines a time period within one day to perform solar caclulations. A Julian Day, start time, and end time are specified.

Tools that use time objects

Area Solar RadiationPoints Solar RadiationSolar Radiation Graphics