Assign index to all records in a table based on date

I'd like to have a field that calculates an index representing a chronological order, relative to all the other records in the field, based on a user-entered date field. Is that possible? 

e.g. I have 5 records and each one has a user entered date that may be different than the record creation date. I'd like a formula field that indicates the chronological order of those records based on the user entered date field. 

Thanks!


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Peter Schultz
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