Talmud for Rosh Hashanah 1:1
משנה ארבעה ראשי שנים הן באחד בניסן ראש השנה למלכים ולרגלים באחד באלול ראש השנה למעשר בהמה ר' לעזר ור' שמעון אומר באחד בתשרי:
From when may one recite Shema in the evening? From the time the Kohanim go in to eat their Terumah (produce consecrated for priestly consumption). Until the end of the first watch, says Rabbi Eliezer. And the Sages say: Until [astronomical] midnight. Rabban Gamliel says: Until the break of dawn. It once happened that his [Rabban Gamliel’s] sons came from a house of feasting. They said to him: We have not recited Shema. He to them: If dawn has not broken, you are obligated to recite it. And it is not only in this case that they said it! Rather, in all cases where the Sages said "only until midnight," the obligation remains until the break of dawn. [e.g.] Burning the fats and limbs [of the sacrifices, on the Temple altar] — the obligation is until the break of dawn. [e.g.:] All [sacrifices] which may be eaten for one day — the obligation is until the break of dawn. If that is so, why did the Sages say, "until midnight?" To distance a person from transgression.
Jerusalem Talmud Nedarim
Since the Mishnah states that “he is forbidden during the year and its intercalary month”, it seems that the year must be counted from Nisan since, if it were counted from Tishre, the intercalary month would be in the middle of the year and it should be obvious that the person imposes a continuous prohibition on himself.? Tishre is the beginning of the year as far as vows are concerned. That you should not say, the beginning of Adar should compensate for Ellul and he would be permitted in Ellul15If a person said, I shall not drink wine for a year, it would imply a prohibition for 12 months. But since he said, this year, the prohibition lasts either 12 or 13 months, as the case may be. The statement of the intercalary month is made to underline the difference between “a year” of twelve months and “this year” of possibly 13 months. If somebody says on New Year’s Day of an intercalary year that he will not drink wine for a year, he will in effect be permitted to drink wine on the first of the coming Ellul. But for this year, he has to observe the additional intercalary month without compensation.; therefore, it was necessary to say that “he is forbidden it and its intercalary [month]”.