如何在objective-c中设备时钟的分钟变化时调用方法

I want to do something like this. When my view load I am showing the server time on my view. and what I want to do is when my device clock minute changes I want to call to the service again and get the server time. Is there any event fire when the device clock's minutes change? Or how can I capture that? Please help me.I want to do something like this. When my view