(for NoteNlp:) The date and time of the note processing. Useful for data provenance.

(for Metadata:) The date and time associated with the metadata

(for Measurement:) The date and time of the Measurement. Some database systems don't have a datatype of time. To accommodate all temporal analyses, datatype datetime can be used (combining measurement_date and measurement_time [forum discussion](http://forums.ohdsi.org/t/date-time-and-datetime-problem-and-the-world-of-hours-and-1day/314))

(for Observation:) The date and time of the observation.

(for Specimen:) The date and time on the date when the Specimen was obtained from the person.

(for ProcedureOccurrence:) The date and time on which the Procedure was performed.

(for Note:) The date and time the note was recorded.

metadata.metadata_datetime#366 AS datetime

note.note_datetime#96 AS datetime

note_nlp.nlp_datetime#117 AS datetime

measurement.measurement_datetime#75 AS datetime

procedure_occurrence.procedure_datetime#170 AS datetime

observation.observation_datetime#125 AS datetime

specimen.specimen_datetime#185 AS datetime