We want to add the descriptions for a few elements in the EvidenceVariable Resource.

participantEffectiveDateTime: A single point in time (e.g. Jan 1, 2020, 0100)

participantEffectivePeriod: An interval (e.g. Jan 1, 2020, 0100 through Jan 30, 2020, 2359)

participantEffectiveDuration: The length of time within an interval (e.g. 30 days)

participantEffectiveTiming: A flexible, complex description of intended or actual time frames