Documentation for Date calculations?

Versions (relevant - OpenSearch/Dashboard/Server OS/Browser):
v2.4 (though likely all)

Describe the issue:

The documentation for the Query DSL/Range Query shows examples of using query values such as:

  • "gte": "now-2d"
  • "gte": "2019/01/01||-1y-1d"

Is there any documentation for the types of calculations that can be made using such syntax? I see || mentioned in the Date/Formats. Would like to see something more definitive as to what is actually supported.