For cellphones, I almost always bother to include the +1 for all numbers [in the US], not just long-distance. That's because the + prefix turns it into a global phone number that works everywhere. The phone network knows how to translate the +1 as needed for your local area. When I first went abroad, it took me a while to figure out how to call a German phone number while in Germany. I had saved it as a 011 49 ... and that doesn't work to call the German phone number when using that cellphone inside the country of Germany even though it's a US T-Mobile SIM card. You have to dial as if you were local to their phone network. I tried dropping the 011 and also the 49 country calling code to call Germany, but it still didn't work. It turns out, German local calls always start with a 0 so I really had to replace the 011-49 with just a 0. However, if I use +49 as the leading prefix, then it still works, in the US, in Germany, or even in India. Any phone number without that + sign is local to the phone network it is started from and will be different depending on your location, but a global phone number always works. It's like starting a file path with / (or C:\ for you Windows folks) and making it absolute instead of starting with the folder name like Documents and assuming it's local to your profile.