Okay, folks,
I realized my questions looked ridiculous in pilots' point of view. I am not a pilot (only took some flight lessons with Cessna 172 before). As some of you replied, I saw the clock in the cockpit now. I thought I studied much about cockpits, but actually not enough. I didn't google "clock in the cockpit" before making the question. Only googled "current time indication, cockpit". I found nothing with the words.
So therefore,
Pilots' gaze may come and go between the clock in the cockpit and MCDU when handling temporal operations (e.g., try to meet ETA to the scheduled time of arrival in the destination airport). So we don't need to worry about the temporal processing with flight deck display (comparison between ETA or RTA and the current time), and the current sole ETA indication on ND is just okay for temporal processing, RIGHT? Maybe no need to add UTC current time in ND. That was my second question.
It seems that we don't have serious problem in using CDU to conduct future mandatory RTA operations. Still I research about potential problems and possible solution in the temporal operations. In the researcher's point of view, reducing human gaze trajectory to monitor information will be beneficial. An research idea of integrating time information on ND is for the benefit. I will appreciate if you guys can tell me how you feel about the idea. Also, if you personally find any potential problem in conducting any kind of temporal operation, please reveal.
Thank you very much folks for your friendly replies. And thank you Clandestino for your rudeness.