formal occasion

基本解释

A:But it's a very casual gathering,not a formal occasion.
可这个聚会很随便，不那么正式。
They wear them when they go out on a date or want something a bit different for a formal occasion.
她们也同样可以穿上和服去约会或出席一些正式的场合，使自己与众不同。
edu.sina.com.cn
And it would be odd for any 53-year-old man to kiss any 77-year-old woman on first acquaintance, let alone a queen, at a formal occasion, and "full on the lips".
对任何一个53岁的男人来说，首次在一个正式场合见到一位77岁的老妇人就“完全嘴对嘴“亲吻她，实在很古怪，何况这位老妇人还是一位皇太后。

And there will actually be a formal occasion in which foreign policy will be debated as part of the presidential campaign debates.
WHITEHOUSE: Press Briefing