The traditional Eucharistic fast from Apostolic times has been since midnight, the beginning of the liturgical day. If you assist at an evening Mass, as on a Holyday of Obligation, the fast prescribed is four hours. If you travel some distance to assist at a fully Traditional Latin Mass or have medical issues. you should consult your traditional Catholic confessor for a dispensation.
http://www.traditio.com/comment/com1907.htm#190718
拝領前断食を始めるのは
前日夜12時＝典礼当日が始まる真夜中０時
夕刻の典礼時は4時間前
旅行、健康上の都合がある場合は伝統的司祭に免除を相談