A lot depends on whether this example is the pattern for all of the instances of multiple dates, or just one possible pattern. If it's always that pattern (and assuming you always want the first date) you could create a calculation that gets the leftmost date:
DATE(LEFT([Date Field], 10))
Or, if you wanted the right-most date:
DATE(RIGHT([Date Field], 10))
I hope that works and you can mark this answer correct. But if the pattern differs at all, that may not consistently work and we might need the examples of the full spectrum of possibilities.
Thank you for the response Joshua I tried the DATE(LEFT([Date Field], 10)) on a sample data set where every row contained the same length and values but having created a calculation, when applied only returned null values
However what I have now found out and is working for me is to initially change the field from Date format to String then using Left([Date Field],10) I get the left most value
All the best