From what i've seen if its the day of, it shows the event in italics, while if its the next day but within the time period it will show it just in regular text.
Also i've noticed there is a 24 hour window in which it shows, not sure if this is obvious common knowledge but its nice to know if you don't already. For example i have 3 things on my calendar for tomorrow. First one is at 4:30pm, then 7pm then 9pm. They will start showing up in my calendar today at those respective times.
Then after midnight tonight they will all turn italic to show they are happening within the current day.
But i don't think there is an option increasing/decreasing that 24 hour time period window