why the field "DateTime" is not the current date of the Server in the table of "CustomPollerStatistics_detail"?

Nowadays,

I defined a Custom Poller of the equipment CPU(Huawei CPU)

why the field "DateTime" is not the current date of the Server in the table of "CustomPollerStatistics_detail"?

So, I add a field named "SysTime" , this default value is : getdate();

why the time of the two datetime-fields value is not synchronous?  

thanks,