Parashas Behar · Aliyah 1 · Passuk 25:08
Chabad.org — English translation + Rashi
Torah Temimah cites Yerushalmi Rosh Hashanah 1:2.
English: “Seven Sabbaths of years.” On the first of Tishrei is Rosh Hashanah for Yovels. From where do we know? Because it is written “and you shall count for yourself seven Sabbaths of years”: just as years and Shemittah years are counted from Tishrei, so Yovels are counted from Tishrei.
Classical derasha (Yerushalmi).
The first of Tishrei is also Rosh Hashanah for Yovel years, parallel to the counting of ordinary years and Shemittah years.