When What Is
Today is Saturday. Saturday is today.
Yesterday was Friday. Friday was yesterday.
Tomorrow is Sunday. Sunday is tomorrow.
This month is February. February is this month.
Last month was January. January was last month.
Next month is March. March is next month.
This year is 2019. 2019 is this year.
Last year was 2018. 2018 was last year.
Next year is 2020. 2020 is next year.
This decade is the Teens. The Teens is this decade.
Last decade was the Oughts. The Oughts was last decade.
Next decade is the Twenties. The Twenties 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?