Carbon vs datetime immutable?

Question

PHP

There are 2 dates

<field name="createdAt" type="carbondatetime" />
 <field name="updatedAt" type="carbondatetime" nullable="true" />

And a huge bunch of options for date formats.
What format for what date?
Why?

Answer 1

everything depends on logic. usually:
- creation date must not change
- modification date must change