I've noticed a buggy behavior of plan mode when using high values of timestamps. This was showing up in a more complex setup but can be reproduced with the following randomly generated minimal (non-)working example.

• test_2023.json has a single job with no TW constraint and a single vehicle with a 2-hours long TW starting today at 9:00 GMT.
• test_2093.json is exactly the same instance but shifted in time 70 years from now (only the vehicle TW differ).

$ diff test_2023.json test_2093.json
14,15c14,15
<         1698138000,
<         1698145200
---
>         3907213200,
>         3907220400

Now using plan mode on those yields different results:

$ vroom -c -i test_2023.json | jq .summary.violations
[]
$ vroom -c -i test_2093.json | jq .summary.violations
[
  {
    "duration": 1845631911,
    "cause": "delay"
  }
]

The delay showing up is on the job step which is clearly wrong. The fact that some delay shows up on a non time constrained task, plus the fact that it happens when significantly increasing the TW values seems to hint to some kind of overflow somewhere.