We ran into issues recently while setting up a php/mySQL server on IIS7, giving the error message - 'It is not safe to rely on the system's timezone settings'. Once the basic installs of php and mySQL had been completed, a phpinfo() request would return:

"It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'America/New_York' for 'EDT/-4.0/DST' instead"

This was a bit of a puzzle for a while, one of those you know is going to be REALLY simple to fix. It turned out to be super, special simple. It was fixed by uncommenting and changing this line in php.ini:

date.timezone = "Europe/London"

If you're in a different timezone, here's a list of European options for you:

Europe

Europe/Amsterdam Europe/Andorra Europe/Athens Europe/Belfast Europe/Belgrade
Europe/Berlin Europe/Bratislava Europe/Brussels Europe/Bucharest Europe/Budapest
Europe/Chisinau Europe/Copenhagen Europe/Dublin Europe/Gibraltar Europe/Guernsey
Europe/Helsinki Europe/Isle_of_Man Europe/Istanbul Europe/Jersey Europe/Kaliningrad
Europe/Kiev Europe/Lisbon Europe/Ljubljana Europe/London Europe/Luxembourg
Europe/Madrid Europe/Malta Europe/Mariehamn Europe/Minsk Europe/Monaco
Europe/Moscow Europe/Nicosia Europe/Oslo Europe/Paris Europe/Podgorica
Europe/Prague Europe/Riga Europe/Rome Europe/Samara Europe/San_Marino
Europe/Sarajevo Europe/Simferopol Europe/Skopje Europe/Sofia Europe/Stockholm
Europe/Tallinn Europe/Tirane Europe/Tiraspol Europe/Uzhgorod Europe/Vaduz
Europe/Vatican Europe/Vienna Europe/Vilnius Europe/Volgograd Europe/Warsaw
Europe/Zagreb Europe/Zaporozhye Europe/Zurich

Other timezones can be found here