When trying to create a new query the Last Modified Date field is showing for selection.
"Image/data in this KBA is from SAP internal systems, sample data, or demo systems. Any resemblance to real data is purely coincidental."
SAP SuccessFactors HXM Suite
This is an expected behavior of the system because the last modified date is a System field used to document when is the last time there was a change and it is already available as a standard on EC side.
Date, Last Modified, Not visible , KBA , LOD-SF-ANA-ADV , Advanced Reporting (ODS) , Problem