It is obvious that there is a time difference between Japan and Greece. So, you are required to adjust your time clock visiting there.
By the way, I usually equip a radio-controlled clock on my left wrist. This kind of gadget is directed to correct the time automatically. Therefore, I have no difficulty to find the exact time whenever I want to know it. However, it cannot receive a precise radio wave of time in foreign countries. Actually, it often became inaccurate after an overseas journey. I decided to leave it at home during this trip.
Then, there were some gadgets other than the wristwatch to let me know the local time.
I use Galaxy S3 powered by Samsung. It was excellent at adjusting the time. Immediately after landing in Greece, it began to gather the data of the position and correct the time without any manual operation. No connection fee was needed. And it returned to direct Japan time after landing Narita International Airport.
(2) Android Tablet
Nexus7 (2012 version) is one of my favorite gadgets. I always carry with me. It did not adjust the time during foreign travel. Even after I connected it to the internet, its time did not alter. Maybe a manual adjustment is required. To be honest, I do not know about Nexus7 LTE version.
My Panasonic Let's Note also did not respond to the place I connected to the internet. It was not surprising considering automatic adjustment of clock time may cause some troubles in PCs.
Kindle Paperwhite (the first model in Japan) was a little troublesome. It adjusted the time clock automatically when I connected it to the internet in Athens. However, it did not recover after returning home. I reset the configuration regarding the clock, but in vain. Finally, I had to initialize the Kindle to correct the time.
To sum up, there is a variety regarding the adjustment of the time. Galaxy S3 seems to be global the most.