When What Is
Today is Sunday. Sunday is today.
Yesterday was Saturday. Saturday was yesterday.
Tomorrow is Monday. Monday is tomorrow.
This month is January. January is this month.
Last month was December. December was last month.
Next month is February. February is next month.
This year is 2021. 2021 is this year.
Last year was 2020. 2020 was last year.
Next year is 2022. 2022 is next year.
This decade is the Twenties. The Twenties is this decade.
Last decade was the Teens. The Teens was last decade.
Next decade is the Thirties. The Thirties is next decade.
This century is the 21st. The 21st is this century.
Last century was the 20th. The 20th was last century.
Next century is the 22nd. The 22nd is next century.
Now are you clear about when what is?