Thanks for volunteering to help with Dutch and welcome onboard!
At the moment we do not have a Dutch localizer actively working on them.
Dutch locale is 70% translated and 0% approved.
We use Crowdin to localize (this is an invite link expiring in one week to join the localization team there).
These are some tutorials to get you started with it:
How to localize CP
How to deal with weird thing in translations
Approving and cleaning existing strings on Crowdin
There is an issue with date formats in some places that I am still investigating because Crowdin seems to be unable to convert the destination date format to the correct PHP format to render via the tag. That should not be concerning however since when I am able to figure things out I will apply the eventual fix on all affected locales.
If you have any questions about Crowdin and localization feel free to ask.