From today on

yes, although "Starting today" sounds better to me...

From today on I will try to be a better person.

Starting today I will try to be a better person.

Yes, very normal, widely seen, also from this day on, from this day forward.

From this day forth, from this day henceforth.

From now on, say "from today on."

What about "From today onwards" as an alternative to "From today on" or is it too formal?

Thanks again for your kind help.

From this day forward, say "from now on."

Does it mean that I should use "from now on" instead of "from this day forward"?

Please clarify.

Thank you.

I suspect Glennn was giving you an example of the usage of "from this day forward", not an instruction.

Unless making a formal proclamation, people usually say:

"From now on I'm going to drive more carefully."

"I think I'll take a different route to work from now on."

Where I live, they say other things as well. "From today on" is not formal.

Where I live, no one says, "From today on . . ." or "From this day forward . . ." or "From this day forth . . ." or From this day henceforth . . ." And the reason no one says it is because it sounds formal. I have yet to hear someone say, "From today on." We say, "From now on . . ."

"You should take the dog for a walk more often, honey."

"You're right. And I will from this day forth."

"Henceforth" is sufficient. Since the definition of henceforth is "from this day on", you needn't precede it with "from this day." That would be redundant.