When one pings you on Facebook at 11 at night, you're immediately calculating the time change and asking 'what are you doing up now?' and finding out she's having a diabetic episode. Or another comments on a photo of food and you realize that it's breakfast time where she lives, and might toy with making those tostadas for lunch or dinner!
A year ago, I never would have been able to tell you what time it is outside the US (except for London and Tokyo) with much speed, it would have required counting back from GMT and adding 5 for my east coast time. Now, I can tell you what time it is in Stockholm, Rome, Adelaide, Germany, Turkey, or Christchurch without thinking. Two of those are thanks to classmates being based there, but the rest are the friends in the computer.
I'm able to convert Fahrenheit to Celsius nearly as fast thanks to the weather conversations, but I need more work on the rest of the metric system. Guess I need to get more help on that front-when they're awake!