CFAbsoluteTimeGetCurrent（）返回的结果在各设备之间是否准确？

I am trying to debug an iPhone app that uses bluetooth for communication. I am basically wondering if the devices should agree on the time down to the millisecond. I am stamping the message when it is sent from one device with CFAbsoluteTimeGetCurrent() and subtracting that from CFAbsoluteTimeGetCurrent() on the other device when the message arrives. Is it safe to assume they are in sync to that granularity? Is there another way to time the messages? I am trying to debug an iPhone app that uses bl