Related על שקלים 3:1

The first of Elul is the beginning of the year for cattle tithing; R. Elazar and R. Shimon say: On the first in Tishrei. [Regarding this] Shimon b. Azzai said: Because some say "first in Elul" while others say “on the first in Tishrei”, the animals born in Elul are tithes for themselves. [What is that supposed to mean]? [Answer:] Five of them were born on Ab and five on Elul, five on Elul and five on Tishrei [or] five in Elul and five in Tishri, so they are not added together; [if he is] five [born] in Tishrei and five in Elul, behold, these are added together. '