Dear native English speakers,
Which would be used?
(a) I'll be playing tennis at this hour tomorrow.
(b) I'll be playing tennis at this time tomorrow.
(c) I'll be playing tennis at this time of hour tomorrow.
(d) I'll be playing tennis at this time of day tomorrow
(e) I'll be playing tennis around now tomorrow.
(f) I'll be playing tennis around this time tomorrow
(g) I'll be playing tennis about now tomorrow.
(h) I'll be playing tennis about this time tomorrow.
I'd say a,b, f and h are OK. a and b sound more formal. h is less formal. To be even less formal (though not strictly correct), you could say "I'll be playing tennis this time tomorrow".