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In general observation class domains, the dates and times (when appliable) observations were collected are represented in variable --DTC. In interventions and events class domains, variable --STDTC is used to represent the start dates and times (when applicable) of interventions and events. In findings class domains, the collection date is often aligned with when the source of the finding was collected (e.g., a specimen for laboratory testing) and may not be aligned with when the finding for the observation was generated (e.g., the date the specimen was assayed, and results were generated). Given this, for consistency, variable --DTC is always used in findings domains to represent the start date/time of an observation and variable --STDTC is not used. Variable --ENDTC is used in all general observation class domains to represent the end date and time (when applicable) of the observation.The variables used to describe time can vary between point-in-time observations (e.g., body weights) and duration-based observations (e.g., food consumption). 

The table below further illustrates the expected use of --DTC, --STDTC, and --ENDTC to represent the timing of observations collected at both single point in times and over intervals of time. X denotes when variables will be used.

When the date/time of collection is reported in any domain, the date/time should go into the --DTC field (e.g., EGDTC for Date/Time of ECG). For any domain based on the Findings general observation class (e.g., lab tests based on a specimen), the collection date is likely to be tied to when the source of the finding was captured, not necessarily when the data were recorded. In order to ensure that the critical timing information is always represented in the same variable, the --DTC variable is used to represent the time of specimen collection. For example, in the Laboratory Test Results (LB) domain, the LBDTC variable would be used for all single-point blood collections or spot urine collections. For timed lab collections (e.g., 24-hour urine collections) the LBDTC variable would be used for the start date/time of the collection and LBENDTC for the end date/time of the collection. This approach allows the single-point and interval collections to use the same date/time variables consistently across all datasets for the Findings general observation class. The following table illustrates the proper use of these variables. Note that --STDTC should not be used in the Findings general observation class and is therefore blank in this table.

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