At the beginning of a sentence, you do not need to add a comma after "yesterday", "tomorrow", "today", "last week", "soon", etc.

At the beginning of a sentence, you don't need a comma after "yesterday", "tomorrow", "today", "last week", "soon", etc.

Yesterday I went to the doctor for a cold.

Similarly, in the middle or at the end of a sentence, commas are typically unnecessary (and sometimes incorrect).

Do you want to play video games with me tomorrow?

When using these expressions as the subject of a sentence, never put a comma after them.

Today is Wednesday.

1. At the Beginning of a Sentence

At the start of a sentence, you can skip the comma with single-word adverbs of time, such as "today", "tomorrow", "yesterday", or "soon".

Today he plans to go to the beach with his friends.

Similarly, we often omit the comma after short phrases and expressions that tell us when something happens (last week, next month, this week, in the previous year, etc.)

Last year we visited Thailand and Indonesia.

Earlier this week the project was cancelled.

But add a comma if the introductory phrase is longer (more than four words).

Three years ago this month, he won the Nobel Prize.

Include also a comma if the introductory word or phrase is followed by a dependent clause.

Tomorrow, if you want to go out or something, just call me.

But do not put a comma if the expression of time is the subject of the sentence.

Today is Olivia's birthday.

Next month is October.

Avoid also the comma when using words such as "yesterday" or "tomorrow" as adjectives.

Yesterday morning we went to the mall.

Tomorrow morning I would like to visit my father.

As mentioned above, we do not add a comma after the adverb of time "now" at the start of a sentence; however, we should place a comma after "now" when using it as a discourse marker. Discourse makers help us organize thoughts, join ideas, etc.

Now, let me say that the situation is getting worse.

2. In the Middle or at the End of a Sentence

Except for emphasis, we do not generally insert a comma before or after an adverb of time, like "today", "tomorrow", or "soon", in mid-sentence.

Don't worry; he'll come next month to help us.

Then tomorrow you'll go to the dentist.

Occasionally, you can place these expressions between commas to add emphasis or interrupt the sentence flow.

I want to ask her out, maybe tomorrow, on a date.

But place a comma before the day of the month when using a date format.

The meeting will be held tomorrow, November 16.

She went to San Francisco on Friday, September 25, 2020, to visit her uncle John.

We do not typically use commas with "afterward", "later", etc.

She moved to London afterward.

I later went to the mall.