When What Is

[About this Article]

Today is Wednesday.  Wednesday is today.
Yesterday was Tuesday.  Tuesday was yesterday.
Tomorrow is Thursday.  Thursday is tomorrow.

This month is December.  December is this month.
Last month was November.  November was last month.
Next month is January.  January is next month.

This year is 2018.  2018 is this year.
Last year was 2017.  2017 was last year.
Next year is 2019.  2019 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?