Get Values from NISysCfgTimestampUTC timestamp using C API

Hello,

I verify External Calibration is supported by the device,

NISysCfgGetResourceProperty(resource, NISysCfgResourcePropertySupportsExternalCalibration, supportsECalBool);

and get a NISysCfgTimestampUTC  timestamp (struct unsigned int u32Data[4]) with zero values.

NISysCfgGetResourceProperty(resource, NISysCfgResourcePropertyInternalCalibrationLastTime, lastExtCal);

My initial thought is I should just grab these values where each signifies year, month, day,

NISysCfgTimestampUTC  typdef to the function below from what I understand converts to seconds from 1970.

NISysCfgValuesFromTimestamp(lastExtCal, secondsSinceEpoch1970, fractionalSeconds);

I get  a large value secondsSinceEpoch1970 = 18446744071626706816 , fractionalSeconds = 0.0000

What am I doing wrong?