How to set effective date in dexterity

[michael]

@flipmcf

obj.effective = datetime(2020, 2, 28, 18, 0) #Feb 28 2020
obj.expires = obj.effective + timedelta(days=3) #March 2 2020

I have tried this but this will cause other problems, e.g
plone.app.layout.viewlets.content.isExpired

    if base_hasattr(self.context, 'expires'):
        return self.context.expires().isPast()

will fail.
And don't know about the indexing side effects.