Is it always a standard 2 weeks? If so, you may not need to even ask respondents to select a date. You can pipe an embedded data field with the current date (for your reference) and then the calculated date of 14 days from the day they complete the survey. You can then use piped text to simply display this to the respondent as Deadline Date is ${e://Field/DeadlineDate}.
Credit for this solution and more information available at this Qualtrics community post and this post from Ohio State University. The solution from Ohio State University also shows you can have multiple dates - if it's not a set 2 weeks you could even calculate a few different dates and just let your respondents select their preferred date from a list (e.g. 12 days, 13 days, 14 days after submission could be 3 answer choices in a multiple choice question for them to pick from).