Dates Related to Observations

Per the OpenMRS data modeling for Observations, it is important to understand the dates associated with stored obs. The list below provides a brief overview of these items:

Encounter.encounter_datetime: The date of the clinical encounter with the patient. In other words, the date that the patient was seen.
Obs.obs_datetime: Each observation has an obs.datetime date associated with it. This item is meant to capture the date that the observation occurred. In other words, the observation date is the date the observation was made, the date the question was asked, the time the sample was drawn, etc. By default, this date is populated with the encounter.encounter_datetime. However, in some cases it is necessary to specify a different date for this item. For example, if a patient has had a lab test done, the lab might have been performed prior to the actual encounter with the patient. In that case, the encounter.encounter_datetime different than the obs.obs_datetime. The obs.obs_datetime, in this situation, is a different date than the encounter.encounter_datetime.
Obs.date_created: The date that the data encounter data was entered into OpenMRS.
Other dates go beyond the scope of the observation, and should be separate observations in and of themselves with their own datetime timestamps. An example of this would be a question to ask the patient's return visit date, which is a concept with a "date" datatype.