I am an undergrad student who has recently taken a course under a professor. I sent him an email last Thursday for confirmation that I will be allowed to register for his course (it has not started yet).
I did not receive a reply for the next two days, but did not find anything amiss in that, since professors do take their time while responding to emails, and the weekend was approaching.
I received a reply three days later on Sunday night with a positive response and some general information about the course and the first class. About 10 minutes later, I received another email as a correction to the first response.
I did see both the emails on my phone late in the night since I can access GMail on it, but I didn't respond yet at the time, since emails typed on the phone seem to have weird formatting at times. So, I decided to respond to the email the next day (today, Monday) on my laptop once my classes are done (this particular class hasn't begun yet).
But today afternoon, I received a rather curt email from the Professor asking me why I haven't responded yet and if I am still interested in taking his class (I very much am). This surprised me since it hasn't even been 24 hours since his last email and the course does not begin until 2 days from now.
I know I should have responded from my phone right when I saw his response last night, formatting issues notwithstanding, and I do tend to procrastinate answering emails, so that is my mistake. But I did not think it would be a big deal.
Of course, now my course of action is to just apologize, but I would like to know if this was an outlier or the standard in academia.
I know that it is common to wait a few days before expecting a response from a professor, but is there a standard regarding student replies to a professor?
If it matters, I am from a country in Asia.