同日 + Event
同日 (tóngrì) means "the same day" and is used in formal or written contexts to indicate that something happened on the same date as a previously mentioned event. It typically appears at the beginning of a sentence to connect two events chronologically. It is more literary than the colloquial 同一天.
会议和展览在同日举行。
huìyì hé zhǎnlǎn zài tóngrì jǔxíng.
The conference and exhibition were held on the same day.
同日,另一场比赛也在北京开始了。
tóngrì, lìng yī chǎng bǐsài yě zài Běijīng kāishǐ le.
On the same day, another competition also started in Beijing.
两位领导人同日发表了声明。
liǎng wèi lǐngdǎorén tóngrì fābiǎo le shēngmíng.
The two leaders issued statements on the same day.