Find most recent date in list of dates

I am trying to display the last pay date for each month. The formula querya returns a list of the pay dates in that month, but I am stuck on how to find the highest date in the list.

//FID 8 = pay date
var text myquery= "{8.GTE.'"&[First of Month]&"'} AND {8.LTE.'"&[Last of Month]&"'}";

var text querya= "{GetFieldValues(GetRecords($myquery),8)}";

Max(
ToDate(Part(ToText($querya),1,";")),
ToDate(Part(ToText($querya),2,";")),
ToDate(Part(ToText($querya),3,";")),
ToDate(Part(ToText($querya),4,";")))

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Anne Martin
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