When I have two meetings: one at 1pm and the other at 3pm, which one is more appropriate?
- I have (two) meetings at 1pm and 3pm.
- I have a meeting at 1pm and 3pm.
I prefer the second one, but rephrased slightly.
I have a meeting at 1pm, and then another at 3pm.
No ambiguity here!
The second one is more clear. The first is fine but is slightly more likely to be misinterpreted.
Both can be said but to avoid the ambiguity, you need to have a pause while telling the first sentence. Or in writing, you may add a 'dash'.
I have (two) meetings (pause) --at 1 pm and at 3 pm.
With no pause, it MAY convey the message that you have two meetings at 1 pm and two meetings at 3 pm.
I can think of an another example in similar context -
I have two cars at home and (at) office
This, to my ears, brings in an ambiguity of having four cars.
I have two cars (pause) --at home and at office OR I have a car at home and another at office.
will mean two cars in total -one at office and one at home.
[However, it's quite obviously understood that one cannot have two meetings at the same time but above, I talked about English and not intellect!]
Also consider StoryMasterQ's opinion. It's straight and good (+1).
Your second option is also fine as it talks about one meeting at 1 pm and one more meeting at 3 pm.