временные интервалы для визитов
т.е. это не конкретный день, а период, в течение которого пациент должен прийти на сдачу анализов
http://www.trialnetworks.com/platform/visit_guide
Using the Visit Calculator, a study coordinator can enter the date of one visit and it generates the target dates for all other visits with precise information about visit windows and other useful notes. The coordinator can adjust dates and instantly see other visits updated to help avoid, for example, holiday scheduling conflicts. Visit Calculator makes it easier to ensure all visits happen within the protocol-specified window, reducing protocol deviations and unevaluable patients.