Q. One who accepts Shabbos an hour early (for the Segula of Tosefes Shabbos, which brings bracha), should the same be done for Yom Tov? Are there any exceptions? Is accepting Shabbos an hour early a Neder?
A. Horav Shlomo Miller’s Shlit’a opinion that the Segulos and Brochos for accepting Yom Tov early, are similar to Shabbos and are equally encouraged.
The early valid acceptance is after the time of Plag.
All good added traditions and minhagim that one decides to accept and keep, should always be taken and done ‘Beli Nedder,” specifically without any promise, vow, oath or similar pledge. The above is usually included in the Hatoras Nedarim declaration on Erev Rosh Hashana.
Rabbi A.Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a