Unexpected results from matcher

[simplenotezy]

Given the following expression:

const futureMatches = cronjsMatcher.getFutureMatches('0 2 * * 0', {
  startAt: new Date().toISOString(),
});

The following output is produced:

[
  '2022-01-12T02:00:00.864Z',
  '2022-01-13T02:00:00.864Z',
  '2022-01-14T02:00:00.864Z',
  '2022-01-15T02:00:00.864Z',
  '2022-01-16T02:00:00.864Z'
]

Which I wouldn't expect. I would expect a list of each Sunday at 02:00 - but perhaps I missunderstand the API?

[simplenotezy]

It seems that this produces the right output: 0 2 ? * 0, however, it just doesn't seem like valid cron syntax: https://crontab.guru/#0_2_?_*_0

[brsanthu]

dow (day of week) and dom (day of month) are very confusing. This confusion comes from, how to interpret when both are specified. Standard seems that if both are specified, then any day that matches either of them (dow or dom) should be considered as a match and many believe the same.

I cannot speak for crontab.guru but specifying * in any field means all values but crontab.guru is treating * as ignore char.

With that details, I think the library is behaving as designed. We documented this in the Readme

Cron expressions indicates time units which all should match for a time to match that expression. Given time matches cron expression if and only if second + minute + day (day of week or day of month) + month + year time units matches.