Getting a time stamp from a Mac thru a USB

Ive seen some pretty clever sketches to get time but they all seem to involve using a shield. I may have even looked right at the answer that Im looking for an because of my Novice status didnt even know it.

I have a little project Ive started, it requires a "time stamp" at the very beginning of the board starting up, so that all events are oriented to the time of day. Im setting millis() to track the time passage from one event to the next but they are of little use without the time of day stamp at the beginning of the log.

Is there a way for my Uno board to retrieve the time of day from my MacMini? with out using a shield?

Yes look at the real time clock examples. One of those sets the real time clock shield or board from your computer. Just don't do the writing to the real time clock chip.