They will be a way of changing the clock but i suspect the setting may be somewhere else. Generally GMT Time of GPS cannot be altered, as the GPS Time dosen't change for british summmer time ect The time should also be accurate. I afaid I cannot tell you how to alter, as i dont have access to a connect system at this time, and as you now they are a lot off menu's, but i would say that i would look for some menu to change to BST To GMT and vise-vesa. Hope that helps, As on my gps system.