Reading and editing other people’s work, there are some issues that crop up over and over. Here’s one of my favourites:
The word AGO means before now. It shouldn’t be used in the past tense.
When King Charles I lost his head he had been crowned only 24 years ago.
This is not okay. It means that Charles was crowned in 1994. It should read:
When King Charles I lost his head he had been crowned only 24 years earlier.
Likewise, the word yesterday means the day before today. Today means this present day.
Tomorrow, next week, next month, next year, last year, last month, last week, the week before last, etc. All these words and phrases relate to the present day, and none of them can be used in the past tense:
When Miriam got married, she had turned 21 only yesterday. Should read:
When Miriam got married, she had turned 21 only the day before.
Mary bought flowers for the house. Today was her fifth wedding anniversary.
Mary bought flowers for the house. It was her fifth wedding anniversary that day.
Michael had been expelled from school the year before last.
Michael had been expelled from school two years earlier.
She knew she was going to have to face her tormentor tomorrow.
She knew she was going to have to face her tormentor the next day.
It’s fine in dialogue, of course, where the speaker is referring to time relative to his/her present.
“I caught a glimpse of a stranger on a Wednesday evening, two years ago.”