Fix returned type around datetime

[thican]

Description

Fix commit 9851ca6 from PR #424, it resolves some linter error reporting.

Checklist

• I have reviewed the contributing guidelines.
• I have included unit tests for my changes or additions.
• [ ] I have successfully run make test-docker with my changes.
• I have manually tested all relevant modes of the change in this PR.
• I have updated the documentation.
• I have updated the changelog.

Questions or Comments

Commit from quite some time, so I am not able today to recreate the test environment, hence why I did not run test through Docker.
However because it does not modify any actual instruction, it should not have any impact.
And no documentation update required.

[jertel]

Thanks for that correction. Will you please update the CHANGELOG with the fix?

[thican]

Okay done, but I think it was better to not update CHANGELOG for this, as it has no impact on instruction because Python language does not check type during runtime (not 100% sure tho).