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Timeframes (referred to as study reference periods), fixed points in time, and other milestones, may be defined in the context of a study as references to which the timing of other collected observations are related. The following will be collected using TIG Collection or CDASH Model Timing variables when references for the timing of other collected observations are defined:

• Start and end dates, and optionally times, of study reference periods.
• Dates, and optionally times, of fixed points in time and/or milestones.

For some studies, a study reference period, study reference points, and/or milestones may be defined per protocol, company policy, standard operating procedures, or other documented procedures. In such cases, the dates (and times when applicable) of the start and end of the study reference period, study reference points, and/or milestones will be collected.

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Relative timing variables are sets of variables that provide information about how the timing of the record relates to either the study reference period or another fixed point in time. CDASH relative timing variables are collected for observations where a date either is not collected or is not available. The CDASH set of variables serve as an indicator (or flag) that the observation's "start" was prior to the study reference period or prior to another fixed point in time OR that the observation's "end" was after or ongoing as of the study reference period or another fixed point in time. The CDASH variables of --PRIOR and --ONGO serve this purpose. How these CDASH flags are translated to SDTM (according to controlled terminology) depends on whether the comparison is against the protocol-defined study reference period or against another fixed point in time serving as the "reference" for the timing of the record. To emphasize, collection of these CDASH relative timing variables is always dependent on the actual date either being prospectively not collected or not available. For more information, see Section 8.1.1, General CDASH Assumptions for Interventions Domains, and Section 8.2.1, General CDASH Assumptions for Events Domains.

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