Do I have to ask permission for a one day leave from graduate school? I am a Masters student in maths in Toronto and changed supervisors one year into my Masters program. My new supervisor was expecting me to to a PhD with him, but within two months of switching to him, I mentioned to him that I would not be pursuing a PhD. I mentioned to him that I haven't decided what to do after my Masters, as I would like to work hard on my Masters thesis and write a good thesis.

Even though I said this, I am spending half my time learning data science because I would like to transition to data science after my Masters. The fact that I have only been putting in a minimal amount of effort to my thesis is reflected in the amount of work I complete every week before my meeting with him.

I have recently decided to fly to Chicago for a networking event in data science, which means that I will not be on campus for one working day of the week and also I will miss my supervisor's group meeting. I have already mentioned this to the course instructor for which I am a TA this term and he's switched my office hours for next week.

Now, the course instructor and my supervisor are in the same research group, and I am afraid to ask my supervisor for a leave for one day because I have been putting in a minimal amount of effort for my Masters thesis.

Should I ask my supervisor for a one-day leave, or should I not tell him and miss the group meeting and just return to work the next day?
In general, it is not a good idea to miss a meeting that you were expected to attend, without giving any notice. It looks unprofessional, and it is annoying and rude to people who made plans based on your attendance at the meeting.

Let your advisor know that you are planning to miss the meeting.