Date Offset Functionality

[chrisknoll]

A new feature to allow users to specify offsets from start_date or end_date for 'query' criteria.

Some considerations:

• The requested offsets should be bound to the same observation period from where the event was found.
• Offsets that produce end_date > start_date will be dropped.

[chrisknoll]

After some back-and-forth, the initial implementation will not do any observation period bounding. For cohort entry events, moving an event outside an observation period will cause it to be dropped. For correlated criteria, you can move the dates anywhere and say 'ignore observation period' and the observation period dates will be ignored.