Which one is valid:
A date field should be in a form 'MM/DD/YYYY'.
or
A date field should be of a form 'MM/DD/YYYY'.
Which one is valid:
A date field should be in a form 'MM/DD/YYYY'.
or
A date field should be of a form 'MM/DD/YYYY'.
in the format is the general expression used in the context.
The definite article the will be needed.
A date field should be in the form 'MM/DD/YYYY'.
The alternate preposition of is acceptable in a similar way.
A date field should be of the form 'MM/DD/YYYY'.