Duplicate Holidays

Hi folks,
There are 3,790 duplicate holidays in the holidays.csv file, when using SiteId and Date as a key.
Some of these duplicates are due to actual coinciding holidays, but others are due to erroneous data (e.g. Christmas Eve is not on 12/25). Has anyone any recommendations for cleaning this up? There are far too many to clean by hand, so I am just going to remove duplicates and hope all is well unless anyone has a better solution.

In order to give the same number of days off per year, some companies “observe” holidays on different dates than the actual holiday if the holiday happens to fall on a weekend.

Is it possible to provide the country location of the site so that we can calculate the missing holidays? Thanks!