Years ago, not last year, as you would assume from the meaning of 'yesterday'. it's much more general. Middle English, not really in use nowadays.
I think back to my golden memories of yesteryear...
by emma December 20, 2004
A word meaning last year.
Yester can also be put in front of other words.
Ex. Yesteryear
Remember yesteryear, when we burned the inside of that garbage can?
by blackblondie13 October 11, 2005
A place that only exists in the brains of Republicans.
"I wish we lived in a place more like the America of Yesteryear, that only exists in the brains of us Republicans." - Ned Flanders, The Simpsons.
by Imakoo April 28, 2006
A question posed by Yossarian in Joseph Heller’s Catch-22 to find out why so many people were working so hard to kill him.

This seemingly rhetorical question is what one asks when one feels that everyone else is asking stupid questions and one wants to join in and/or point out how obviously stupid their questions are. Or, merely, because one wants to find out why so many people are working so hard to kill oneself.
Yossarian was a collector of good questions and had used them to disrupt the educational sessions Clevinger had once conducted two nights a week in Captain Black's intelligence tent with the corporal in eyeglasses who everybody knew was probably a subversive. Captain Black knew he was a subversive because he wore eyeglasses and used words like panacea and utopia, and because he disapproved of Adolf Hitler, who had done such a great job of combating unAmerican activities in Germany.

Yossarian attended the education sessions because he wanted to find out why so many people were working so hard to kill him. A handful of other men were also interested, and the questions were many and good when Clevinger and the subversive corporal finished and made the mistake of asking if there were any.

“Who is Spain?”

“Why is Hitler?”

“When is right?”

“Where was that stooped and mealy-colored old man I used to call poppa when the merry-go-round broke down?”

“How was Trump at Munich?”

Hi-ho beriberi!”

and “Balls!” all rang out in rapid succession, and then there was Yossarian with the question that had no answer:

“Where are the Snowdens of yesteryear?”
by Jill Harris April 26, 2005
When referring to a day from 1 year to 4 years ago; but not any specific day at all. Commonly used during 4am conversations with a 4 year old, asking you if you remember something you weren't around for.
'Eden? Do you remember yesteryear... when Booty stole my purple spider?'
'No, Beans. I don't think I was there for that.'
by edeninoctober June 27, 2021