Use AsDateTime to read the value of the field's data into an object or variable of type TDateTime, or to assign a TDateTime value to the contents of the field. TField does not support TDateTime values, and raises an exception when an attempt is made to get or set the AsDateTime property. 

Descendants of TField that represent datetime (timestamp) fields or that support conversions between the field's Value property and a TDateTime value, override AsDateTime to read and write the value of the field as a TDateTime value. 

DataType 

Value 

AsSQLTimeStamp