Growing up in the 1980s in New York City, I understood a plain "later" to mean "later in the same day", as in the examples below. As an adult, I lived in St. Louis, met people from many more places, and participated in online fora, and understand it to mean "any time later, even not the same day". Is the difference temporal (1980s versus 2000s and 2010s)? geographical (New York versus the rest of the United States, or something)? some combination of those? something else? Perhaps the "later the same day" meaning was just my own idiolect?
I should note that this applies only to the future tense, and not to sentences like "Later, he returned home, only to find" or "he later passed away from the same disease", both of which mean any time later, not necessarily the same day, even to 1980s me.
- Can I come by later?
- What are you doing later?
- See you later!
- I can look it up later.
- Remind me later.
I should note also that my memories of 1980s me's English may well be cloudy.