YOU SAID:

I rode a donkey for my uncle at his birthday.

INTO JAPANESE

私は叔父の誕生日にロバに乗った。

BACK INTO ENGLISH

I rode a donkey on my uncle's birthday.

INTO JAPANESE

私は叔父の誕生日にロバに乗った。

BACK INTO ENGLISH

I rode a donkey on my uncle's birthday.