I've found that there's always a time discrepancy between various clocks. Even the two clocks in t's office show different times. The clock in the waiting room is 10 minutes off from my phone's clock...
I'm always early (I hate getting to appointments late), but my t is regularly late. she seems flex on the time though. She's never kicked me out, or shorted me on my time. A previous t was always about 20 minutes late, but she would end at the time we would have had she not been late. as difficult as it was for me to bring up (I hate confrontation), I talked to her about it. she agreed that it was problematic, and it was "her bad". Sessions lasted the correct amount of time after that, though she was still always 20 minutes late. I just started adjusting my arrival time so I wasn't waiting for 35 minutes before sessions.
What prevents you from wanting to talk to t about your time concerns? If it's big enough to prompt you to leave t, then I assume it's big enough to address with him. Is there another reason you want to leave t, and this is a convenient excuse? Or is confrontation difficult for you also? Or is there Some other reason you don't want to talk to him about it?