 Although the moment of the traditional Hebrew calendar "molad" is announced in synagogues on the "Shabbat" prior to each month (except before "Tishrei"), its only relevance to the present day fixed arithmetic lunisolar Hebrew calendar is that the "molad" of the month of "Tishrei" determines the date of the New Year Day ("Rosh Hashanah"), subject to possible postponements of 0, 1 or 2 days (depending on certain postponement rules, also see external link).Traditionally the announced or printed "molad" moment is quoted in terms of the hours, minutes, and 18ths of a minute (parts) elapsed from mean sunset, because Hebrew calendar days begin at sunset.Some printed sources subtract 6 hours to convert the "molad" moment to "civil" time, but doing so causes the Hebrew weekday to be wrong 25% of the time (whenever the "molad" moment is between sunset and midnight).