Is “today” followed by a comma?

[sitifan]

If “today” comes at the beginning of a sentence and acts as an adverb, then a comma would be necessary.
https://linguaholic.com/linguablog/comma-after-today/

Do native speakers agree with the above rule?

 

[Rover_KE]

I do.

 

[emsr2d2]

In general, a time marker at the start of a sentence is followed by a comma.

Today, I'm going swimming.
Tomorrow, they'll organise a party.
This week, I've played tennis five times.
Last year, he failed his driving test twice.
In an hour, I'll have finished my homework.
An hour ago, the sun set.

 

[5jj]

In general, a time marker at the start of a sentence is followed by a comma.
.

I agree, though I have to admit that I don't always use one, and I don't really notice if others don't.

 

[jutfrank]

I use a comma, and I teach my students to use one too. But is it 'necessary'? Plenty of writers and editors would think not.