The VRayGeoSun node allows you to set the position of the V-Ray Sun for a specific place in the world at a given time.
Manual position - when this option is selected the user can specify the position of the V-Ray Sun manually
Manual up vector - allows you to specify a vector which will be considered as an "up" direction. If disabled the up direction will be specified by Maya and it will be either the Y or Z direction.
Distance to target - allows you to specify the distance between the scene and the sun. This parameter can be used if we want to simulate a scene that is at a level different from the sea level.
Latitude - specifies the geograpic latitude of the point at which the scene is situtated.
Longitude - specifies the geographic longitude of the current point at which the scene is situated.
Year/Month/Day - use these settings to specify the date at which you want the sun position simulated
Day Value - allows you to specify the date by setting the number of the day (1-365)
Time Zone - specify the time zone
Local Hour/Local Minute/Local Second - allows you to specify the time in hours. minutes and seconds at which the sun possition will be simulated.
Hour Value - specifies the time as a float value between 0 and 24.