1. REST API
  2. A Note About Date Ranges

Types of data that are date ranges are serialized to JSON as an object with bounds:

{
  "bounds": "[)",
  "end": "2016-09-16",
  "start": "2016-09-15"
}

Note that since date of service can span over multiple days (for example, a hospital stay), it is stored as a range.

In the text form of a range, an inclusive lower bound is represented by “[” while an exclusive lower bound is represented by “(”. Likewise, an inclusive upper bound is represented by “]”, while an exclusive upper bound is represented by “)”

For more details and examples, please consult the PostgreSQL documentation