always serialize date as only date, stripping time

[ucarbehlul]

Type of change

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• [x] Bug fix (non-breaking change which fixes an issue)
• [x] This change requires a documentation update

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[ucarbehlul]

I realized the title may be wrong after my latest changes, basically this PR will allow date time strings coming from backend to be accepted as date too. This is useful if we are simply calling JSON.stringify on a JS date object and parsing that back later on.