West Hawaii Today: Matt Calkins: MLB’s robot umpires are taking over. Here’s why that’s a good thing. The Week on MSN: Big-league robot umpires are set to alter baseball Matt Calkins: MLB’s robot umpires are taking over.

Understanding the Context

Here’s why that’s a good thing. The phrases " on tomorrow," " on today," and " on yesterday " are commonly heard in the southern region of the United States. They are acceptable in casual speech and other informal contexts, but should not be used in formal contexts such as academic writing. american english - Origins and history of "on tomorrow", "on today ...

Key Insights

3 “Earlier today” is a totally correct way to refer to a point in time between the beginning of the day and the current time. Because it refers to a moment in the past, it can be used with the past tense, as you did in your example. I think it is a good question. When there is yesterday morning and tomorrow morning, why have an exception for this morning (which means today's morning)? Yes, idiom, but I actually do like idiomatic extensions like these - as long as everybody knows what is meant and no grammar or semantic rules are violated...

Final Thoughts

The 2002 reference grammar by Huddleston and Pullum et al., The Cambridge Grammar of the English Language, would consider words like yesterday, today, tonight, and tomorrow as pronouns (specifically, deictic temporal pronouns). Related info is in CGEL pages 429, 564-5.