I've just gone through the ritual with all of mine. Three had already set themselves automatically (the GBX-100s and GMW-B5000), the DW-M5610s and GA-2100s needed DST switching on (the 5610s have an auto setting but it never seems to work even if WT is set to London - maybe it requires a radio sync) and the others (5600/5700) don't have a DST setting so needed manually adjusting by an hour. All were pretty easy to do though - what model G-Shock do you have?
My Antman has radio sync but I'd have to go to Japan to see if it works. It was Casio's first atomic model. Only designed to receive from the Fukushima transmitter
I've just gone through the ritual with all of mine. Three had already set themselves automatically (the GBX-100s and GMW-B5000), the DW-M5610s and GA-2100s needed DST switching on (the 5610s have an auto setting but it never seems to work even if WT is set to London - maybe it requires a radio sync) and the others (5600/5700) don't have a DST setting so needed manually adjusting by an hour. All were pretty easy to do though - what model G-Shock do you have?