Holy Days of Obligation for the U.S.: https://calendar.google.com/calendar/ical/a655b7f43c454d7ec30d94e6ab91d19ebc5920aa6070aeafbf1bdb5df47e9562%40group.calendar.google.com/public/basic.ics
First Class Feasts (Minus Holy Days of Obligation for the U.S.): https://calendar.google.com/calendar/ical/0008ec75e1cee4e325c3fa5da79e70554276fb103d842699193be296537e5d27%40group.calendar.google.com/public/basic.ics
Traditional Penitential Days for the U.S.: https://calendar.google.com/calendar/ical/9ad5423ed06610ab8a3fa78036bfa0f97b6db87abd506e752481937e1d768cff%40group.calendar.google.com/public/basic.ics