Here comes another possibility using regex, probably the shortest implementation would be version 2 below, using additionally informat() in a formula. Once you read the information from the date string, there are many ways to convert it into a numerical date.
If you have the date numerically in Excel, it would be better, to change format in Excel such that JMP can read.
regex is great, I love it!
Names Default To Here( 1 );
// AA for conversion of month
month_AA = Associative Array(
{"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"},
{"01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12"}
);
date_str = "Wednesday, November 18, 2020, 12:45:00 PM";
date_str = "Friday, November 20, 2020, 8:10:00 AM";
regex_str = "(\w+), (\w+) (\d+), (\d+), (\d+):(\d+):(\d+) (PM|AM)";
// 1st version generating a list and building string thereof
date_component_lst = Regex Match( date_str, regex_str );
date_component_lst[6] = char(num(date_component_lst[6]) + match(date_component_lst[9], "AM", 0, "PM", 12));
date_str1 = date_component_lst[5] || "-" || month_AA[date_component_lst[3]] || "-" || date_component_lst[4] || "T" || date_component_lst[6] || ":"
|| date_component_lst[7] || ":" || date_component_lst[8];
// 2nd version generating a string, to be used by "Parse Date ()" do directly convert it into a date
date_str2 = Regex( date_str, regex_str, "\3 \2 \4 \5:\6:\7 \8" );
Georg