"0 1 30 3 *" creates infinite loop

[AndreMaz]

Description

The following snippet blocks the process

import { CronJob } from "cron";
const job2 = new CronJob(
  "0 1 30 3 *",
  function () {
    console.log("You will see this message every second");
  }, // onTick
  null, // onComplete
  false, // start
  "Europe/Lisbon" // timeZone
);

console.log(job2.nextDates(1));

Expression at crontab.guru

What causes the issue is the fact that in Portugal the daylight savings starts at Mar 30 so the 01:00 does not actually exist.

Expected Behavior

Next execution date to be returned or an error/ warning to be shown

Actual Behavior

The process hangs forever

Possible Fix

Steps to Reproduce

Context

Your Environment

• cron version: 3.2.1
• NodeJS version: v20.14.0
• Operating System and version: Ubuntu LTS 24.04

[AndreMaz]

Attached the debugger and tried to see what's going on.

Turns out that it gets "stuck" in while(true) {} statement in getNextDateFrom() method

Added a console.log to see the dates that it was generating. Here's the list:

2025-03-30T00:00:00.000+00:00 86400000
2025-03-30T02:00:00.000+01:00 90000000
2025-03-30T03:00:00.000+01:00 93600000
2025-03-30T04:00:00.000+01:00 97200000
2025-03-30T05:00:00.000+01:00 100800000
2025-03-30T06:00:00.000+01:00 104400000
2025-03-30T07:00:00.000+01:00 108000000
2025-03-30T08:00:00.000+01:00 111600000
2025-03-30T09:00:00.000+01:00 115200000
2025-03-30T10:00:00.000+01:00 118800000
2025-03-30T11:00:00.000+01:00 122400000
2025-03-30T12:00:00.000+01:00 126000000
2025-03-30T13:00:00.000+01:00 129600000
2025-03-30T14:00:00.000+01:00 133200000
2025-03-30T15:00:00.000+01:00 136800000
2025-03-30T16:00:00.000+01:00 140400000
2025-03-30T17:00:00.000+01:00 144000000
2025-03-30T18:00:00.000+01:00 147600000
2025-03-30T19:00:00.000+01:00 151200000
2025-03-30T20:00:00.000+01:00 154800000
2025-03-30T21:00:00.000+01:00 158400000
2025-03-30T22:00:00.000+01:00 162000000
2025-03-30T23:00:00.000+01:00 165600000
2025-03-30T00:00:00.000+00:00 86400000 <----- WE'RE BACK TO SAME DATE
2025-03-30T02:00:00.000+01:00 90000000
2025-03-30T03:00:00.000+01:00 93600000
2025-03-30T04:00:00.000+01:00 97200000
2025-03-30T05:00:00.000+01:00 100800000
2025-03-30T06:00:00.000+01:00 104400000
2025-03-30T07:00:00.000+01:00 108000000
2025-03-30T08:00:00.000+01:00 111600000
2025-03-30T09:00:00.000+01:00 115200000
2025-03-30T10:00:00.000+01:00 118800000
2025-03-30T11:00:00.000+01:00 122400000
2025-03-30T12:00:00.000+01:00 126000000
2025-03-30T13:00:00.000+01:00 129600000
2025-03-30T14:00:00.000+01:00 133200000
2025-03-30T15:00:00.000+01:00 136800000
2025-03-30T16:00:00.000+01:00 140400000
2025-03-30T17:00:00.000+01:00 144000000
2025-03-30T18:00:00.000+01:00 147600000
2025-03-30T19:00:00.000+01:00 151200000
2025-03-30T20:00:00.000+01:00 154800000
2025-03-30T21:00:00.000+01:00 158400000
2025-03-30T22:00:00.000+01:00 162000000
2025-03-30T23:00:00.000+01:00 165600000

Unfortunately I don't have enough knowledge about lib internals to solve this issue.

@sheerlox can you take a look at this?

[intcreator]

we rely on Luxon for most of our international date/time support so it's possible this is due to Luxon not handling that time period correctly