I've only ever seen regional variations to specific saint's feastdays, such as the one-day difference in the commemoration of Greatmartyr Catherine in the Greek calendar and everyone else's (and this has nothing to do with OC/NC).
Another which comes to mind is the feast of the repose of St John Chrysostom (September 14). As this date is also that of the Exaltation of the Cross, one of the twelve great feasts, the Church as a whole has chosen to celebrate St John's feast the day before, to avoid the clash. Likewise, the Greek church also transposes the feast of Greatmartyr St George to Bright Week, if the saint's feast falls during Holy Week.