0 25 7 4-22 8 1-5 2025 should not run on Sat or Sun, but it does

[Steve-Mcl]

Hi @jaclarke - I hope you are well.

It has been reported via my Node-RED Node that the expression 0 25 7 4-22 8 1-5 2025 ran on a Saturday.

Indeed, as I run this expression today on a Saturday, it indicates the next date will be tomorrow, Sunday.

example: Ran at 17:35 BST

const cronosjs = require('cronosjs')
const expression = cronosjs.CronosExpression.parse('0 25 7 4-22 8 1-5 2025', undefined)
console.log(expression)
/*
CronosExpression {
  cronString: '0 25 7 4-22 8 1-5 2025',
  seconds: [ 0 ],
  minutes: [ 25 ],
  hours: [ 7 ],
  days: DaysFieldValues {
    lastDay: false,
    lastWeekday: false,
    days: [
       4,  5,  6,  7,  8,  9, 10,
      11, 12, 13, 14, 15, 16, 17,
      18, 19, 20, 21, 22
    ],
    nearestWeekday: [],
    daysOfWeek: [ 1, 2, 3, 4, 5 ],
    lastDaysOfWeek: [],
    nthDaysOfWeek: []
  },
  months: [ 8 ],
  years: YearsField {
    field: '2025',
    first: 1970,
    last: 2099,
    _items: [ [FieldItem] ]
  },
  skipRepeatedHour: true,
  missingHour: 'insert',
  _warnings: null,
  timezone: undefined
}
*/
expression.nextDate() // 2025-08-10T06:25:00.000Z -- 10th Aug is a Sunday

I would greatly appreciate a fix but I understand if you do not have the time or inclination so a pointer to where I could fix this and I will fork and fix it myself would be equally good.

Thanks as always, Steve.

[Steve-Mcl]

I added a test that demonstrates this:

test("At 07:25, between day 4 and 22 of the month, Monday through Friday, only in August, only in 2025 (0 25 7 4-22 8 1-5 2025)", () => {
  expect(
    CronosExpression.parse("0 25 7 4-22 8 1-5 2025").nextNDates(
      new Date(2025, 7, 8, 6, 0, 0), // August 8, 2025 06:00:00
      10
    )
  ).toEqual([
    new Date(2025, 7, 8, 7, 25, 0), // Fri 8th Aug 2025 07:25:00 - 1
    // skip sat
    // skip sun
    new Date(2025, 7, 11, 7, 25, 0), // Mon 11th Aug 2025 07:25:00 - 2
    new Date(2025, 7, 12, 7, 25, 0), // Tue 12th Aug 2025 07:25:00 - 3
    new Date(2025, 7, 13, 7, 25, 0), // Wed 13th Aug 2025 07:25:00 - 4
    new Date(2025, 7, 14, 7, 25, 0), // Thu 14th Aug 2025 07:25:00 - 5
    new Date(2025, 7, 15, 7, 25, 0), // Fri 15th Aug 2025 07:25:00 - 6
    // skip sat
    // skip sun
    new Date(2025, 7, 18, 7, 25, 0), // Mon 18th Aug 2025 07:25:00 - 7
    new Date(2025, 7, 19, 7, 25, 0), // Tue 19th Aug 2025 07:25:00 - 8
    new Date(2025, 7, 20, 7, 25, 0), // Wed 20th Aug 2025 07:25:00 - 9
    new Date(2025, 7, 21, 7, 25, 0), // Thu 21st Aug 2025 07:25:00 - 10
  ]);
});

This is the result:

 FAIL  tests/simple.test.ts
  ● At 07:25, between day 4 and 22 of the month, Monday through Friday, only in August, only in 2025 (0 25 7 4-22 8 1-5 2025)

    expect(received).toEqual(expected) // deep equality

    - Expected  - 4
    + Received  + 4

      Array [
        2025-08-08T06:25:00.000Z,
    +   2025-08-09T06:25:00.000Z,
    +   2025-08-10T06:25:00.000Z,
        2025-08-11T06:25:00.000Z,
        2025-08-12T06:25:00.000Z,
        2025-08-13T06:25:00.000Z,
        2025-08-14T06:25:00.000Z,
        2025-08-15T06:25:00.000Z,
    -   2025-08-18T06:25:00.000Z,
    -   2025-08-19T06:25:00.000Z,
    -   2025-08-20T06:25:00.000Z,
    -   2025-08-21T06:25:00.000Z,
    +   2025-08-16T06:25:00.000Z,
    +   2025-08-17T06:25:00.000Z,
      ]

[Steve-Mcl]

Actually, I missed the obvious - CRON typically ORs the expression so your lib is doing the right thing by convention

Sorry for the noise 🤦‍♂️

[jaclarke]

Yeah, it's kind of a weird quirk of cron that the 'day of month' and 'day of week' fields are OR'ed together, but then all the other fields act like they're effectively AND'ed.

You can get close to what you want with the nearest weekday modifier: 0 25 7 4-22W 8 * 2025, but that could still 'spill out' of the 4-22 range depending on how the weeks line up. So I think the only way to do it would be to specify just one of the 'day of ...' fields in the cron expression, and do the other check in the callback function.

[jaclarke]

This seems like a reasonable use case though, so I've added an option to allow 'day of' fields to be ANDed together: #33. I'm open to better suggestions for the option name, I'm not sure that intersectDayOfFields is the most intuitive name.