I like giving time spans.

“I’ll be there between 4 and 5”.

Four is when I think I’ll be there (after working in potential delays*, etc). Five is buffer time in case I get stuck in traffic or something else comes up. The buffer means I’m not rushed if something comes up, which means I’m more relaxed and less liable to make bad decisions.

If I can, I’ll tighten the time period.

*yes, I double-dip how long I think I may be delayed. Better to be potentially early than late. At least if you’re early, you can get a coffee somewhere and wait it out.