If you want to find out whether two events are within 14 days of each other without caring which comes first then you ought to be able to write:

abs((event_1.date - event_2.date).days) <= 14

Rather than having to write:

((event_1.date - event_2.date).days <= 14) & ((event_1.date - event_2.date).days >= -14)

In fact, once we close this related issue, you really ought to be able to write:

abs(event_1.date - event_2.date) <= days(14)

Implementing this is a matter of adding a Fuction.Abs operation to the query model and in the query language supporting the __abs__ magic method on numeric series. Adding appropriate spec tests should drive out the rest of the implementation.