Ftsearch on multivalue date field

Hello I am trying to perform a ftsearch on a multivalue date field

so I have the search query FIELD dtDate = 2007/07/07 but it finds only documents who have dtDate with a single value. I want to find also the documents who have multiple values in field dtDate (e.g. 2007/06/06 and 2007/07/07) but contains does not work in date fields, only in text fields.

any suggestions how should I do that ?

Thank you !

Adrian