use ISO-8601 date format for direct yaml parsing

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.45%. Comparing base (27a8ebf) to head (bc1edb5).

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[nick-harder]

@maurerle depending on users not to forget T and followi this exact format is somehow not very intuitive. Is there some specific reason for this?

[maurerle]

Mostly just me wondering, why the yaml does not read this into datetime directly ^^ So we can keep the current behavior in favor of usability.