YOU SAID:

I am going to be late to the meeting today.

INTO JAPANESE

私は今日、会合に遅刻するつもりです。

BACK INTO ENGLISH

I am going to be late for the meeting today.

INTO JAPANESE

私は、今日の会議に遅刻するつもりです。

BACK INTO ENGLISH

I'm late for today's meeting.

INTO JAPANESE

今日の会議に遅れてしまう。

BACK INTO ENGLISH

I'm late for today's meeting.