Using the NPM edts library to show how you might use approximate or uncertain dates in EDTF format with a supporting library contrasting it with an interval in EDTF form. Answering this tweet: https://x.com/alllexist/status/1845810486769508728

edts.js

import edtf, { Date, Interval } from 'npm:edtf@4.6.0';

const approxStartDate = edtf('2024-10-14~');
const uncertainDate = edtf('2024-10-14?');
const interval = edtf('2024-10-11/2024-10-16');

console.table([
  approxStartDate.edtf,
  approxStartDate.min,
  approxStartDate.max,
  approxStartDate.approximate,
  approxStartDate.uncertain,
  approxStartDate.covers(approxStartDate),
  approxStartDate.covers(uncertainDate),
  approxStartDate.covers(approxStartDate.next()),
])

console.table([
  uncertainDate.edtf,
  uncertainDate.min,
  uncertainDate.max,
  uncertainDate.approximate,
  uncertainDate.uncertain,
  uncertainDate.covers(uncertainDate),
  uncertainDate.covers(approxStartDate),
  uncertainDate.covers(uncertainDate.next()),
])

console.table([
  interval.edtf,
  interval.min,
  interval.max,
  interval.approximate,
  interval.uncertain,
  interval.covers(uncertainDate),
  interval.covers(approxStartDate),
])

stdout

┌───────┬───────┬───────────────┐
│ (idx) │ value │ Values        │
├───────┼───────┼───────────────┤
│     0 │       │ "2024-10-14~" │
│     1 │       │ 1728864000000 │
│     2 │       │ 1728950399999 │
│     3 │   255 │               │
│     4 │     0 │               │
│     5 │       │ true          │
│     6 │       │ true          │
│     7 │       │ false         │
└───────┴───────┴───────────────┘
┌───────┬───────┬───────────────┐
│ (idx) │ value │ Values        │
├───────┼───────┼───────────────┤
│     0 │       │ "2024-10-14?" │
│     1 │       │ 1728864000000 │
│     2 │       │ 1728950399999 │
│     3 │     0 │               │
│     4 │   255 │               │
│     5 │       │ true          │
│     6 │       │ true          │
│     7 │       │ false         │
└───────┴───────┴───────────────┘
┌───────┬─────────────────────────┐
│ (idx) │ Values                  │
├───────┼─────────────────────────┤
│     0 │ "2024-10-11/2024-10-16" │
│     1 │ 1728604800000           │
│     2 │ 1729123199999           │
│     3 │ undefined               │
│     4 │ undefined               │
│     5 │ true                    │
│     6 │ true                    │
└───────┴─────────────────────────┘