I'm not sure I understood your question. If you have set the type via the field declaration it should be set. However, the automatic parsing of the string value, if such is used, does not support all of the possible custom date formats. If the date is not parsed and is still shown as a string, then maybe you need to set a custom parse function via the field declaration in which to convert the input string to a Date instance.
If you continue to experience difficulties please open a separate support request in which to provide as much information about the issue and your setup as possible. A small runnable sample will be appreciated.
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