I don't think being in different time zones was ever a problem. The only glitch I ever experienced with Skype would have to be when my laptop was connected to the mains without a battery pack and I accidentally disconnected the cable while I was still logged in onto Skype. After many attempts I couldn't log back into Skype and so had to reinstall my OS and wipe whatever my laptop had on it. No program is ever without glitches, but the ones for Skype aren't ones normal people would be able to find.