How to decide whether to read 「昨夜」 as 「さくや」 or「 ゆうべ」?


I found [an answer saying that 「さくや」is the correct reading of
「昨夜」](https://japanese.stackexchange.com/a/278/4623), but despite that I often
encounter it as「ゆうべ」.

Is there a difference in meaning or are both readings interchangeable?




Both are correct readings. It depends a lot on the context, but ゆうべ is
informal and さくや is formal.

The same can be seen in 明日 with あす and あした, or in 昨日 with きのう and さくじつ.




Both are correct readings. It depends a lot on the context, but ゆうべ is
informal and さくや is formal.

The same can be seen in 明日 with あす and あした, or in 昨日 with きのう and さくじつ.

