英和辞典
  
thirtieth
θə́ːrtiiθさ~ティエす
名詞形容詞
30番目(の), 第30の(人・物); (月の)30日  ⦣ 30th と略す.
the 30th of May
the 30th of May
5月30日
It was his thirtieth birthday last week.
It was his thirtieth birthday last week.
先週は彼の30回目の誕生日でした.