Need a good word for "parts of the day"

Solution 1:

It may be too technical, but in my work it's common to refer to dayparts (Business Dictionary). Even in a less technical situation, morning, afternoon etc are often referred to as dayparts.

Solution 2:

Where I grew up in Boston, Massachusetts, we referred to this as "time of day."

What time of day do you like best? Night time.

What time of day do you usually eat breakfast? Morning.

What time of day do you feel most relaxed? In the Evening, after I get home from work.

There are probably some parts of the English speaking world where they habitually call it something else, but "time of day" should be intelligible to any native speaker of English.

Solution 3:

There is no specific single word, but I think calling it "period of the day" would be more specific and people would not confuse it with.

For instance, someone could write "eating" or "going to the gym"

I did search for it for a good half hour...