normalised FMRIB date/time routines
the fmrib.normalisedDate and fmrib.normalisedAcquisitionTime routines are prroducing values of -9.25061829346198e+18 instead of NaN
the fmrib.normalisedDate and fmrib.normalisedAcquisitionTime routines are prroducing values of -9.25061829346198e+18 instead of NaN