A date type question requires three components of the date to be specified: year, month, day. If any of them is not known, the interviewers may not enter the other ones, even if they are known.
When this is not acceptable, date type question should not be used. Instead consider one of the following alternatives:
- Three separate questions;
- Patterned text question, with pattern specified as ####-##-##
- Categorical question with year-month combinations, such as: