I'm having a really bad day.

我今天倒霉透了。

《牛津词典》

It had been a really bad day.

那真是很坏的一天。

youdao

I still have those gifts, and when I've had a really bad day.

我依然保存着那些礼物，当我遇到一个特别糟糕的日子里，通读它们。

youdao

Many gunmen have a clean criminal history - they are just having a really bad day, he says.

BBC: US gun debate: Could Obama's guns plan work?

Having a fresh CV on-hand can be just the tonic for a really bad day at work, or worse unexpected layoffs.

FORBES: Spring Clean Your Career: Online And Offline Quick-Fixes

Each is considered "Crit-One-R" -- meaning a cable and its twin would have to both fail to make for a really Bad Day.

CNN: Challenger explosion