1var exdate = 33970; // represents Jan 1, 1993
2var e0date = new Date(0); // epoch "zero" date
3var offset = e0date.getTimezoneOffset(); // tz offset in min
4
5// calculate Excel xxx days later, with local tz offset
6var jsdate = new Date(0, 0, exdate-1, 0, -offset, 0);
7
8jsdate.toJSON() => '1993-01-01T00:00:00.000Z'
9