The Medication, Order datatype currently only contains a start datetime and an end datetime, both of which are intended to map to the order's author datetime.

An order, however, typically has two meaningful datetime values: the time it is signed, and the time it becomes active.

In most cases, those times are the same – the order becomes active at the time it is signed. But the significant exception is the case where an order is signed in advance, and only becomes active when it is released or activated. This commonly occurs when a surgeon writes orders in advance of a surgical procedure. The signed time is before the day of surgery, and the active time is the time it is released (usually by a nurse) and carried out.

Therefore, the Medication, Order datatype should have a signed datetime and an active datetime in order to differentiate between the two.

We may also want to consider retiring the existing start datetime attribute, but this should be treated as a separate issue after signed datetime and active datetime are added. Existing measures are currently using start datetime so they will need to be republished using the new attributes before we can remove the existing attributes.

(Suggested by hbregman)