The date when a stage in the design, creation or manufacture of an object took place.
How to record
It may be necessary to use more than one unit of information to describe this date, eg a range of dates or a textual expression of the date as well as the production stage which the date is related to. Descriptions of these units of information are gathered together under the Date heading. Use Date – period to record non-numeric dates and eras relating to an object’s production.
As for Date.
As many times as required for an object.