At around 4 pm Monday, a company I applied to almost a month ago suddenly replied that they would like to interview me on Thursday. However, I am in a class and busy doing homework throughout that day so didn't see and respond to that email at 11:45 am today (Tuesday). As of now (2:30 pm on Tuesday) there is no response to my confirmation of that interview request like "see you soon" from that company. Should I be worried?
So, they sent an email close to the end of the working day, you responded the following day, before midday.
Completely fine. This is pretty standard.
If you are super worried, you could always follow up with a Phone Call:
"Hey, just calling to confirm my Interview is scheduled for this time/date?" - which is completely fine.
Should I be worried?
It took you almost 20 hours to reply to their original message because you were occupied with other things. It has been less that 3 hours since they would have received your reply. Just like you, they can be occupied with other things.
Wait it out until tomorrow, and if you have not heard back you should reach out to them ( with a phone call ) for a follow up since the interview is presumably the next day.
You shouldn't worry! During an interview process and after the first two interviews, I was waiting for a reply. Almost 2 weeks passed, got an e-mail at almost 8pm to schedule the final interview (acceptance and discussion of terms) on the next day. They of course apologised for the delay and time.
In my opinion, a company cannot expect someone to give/do more than what they themselves give/do.
I applied to almost a month ago suddenly replied (4 PM Monday)
Respond to that email at 11:45 am today (Tuesday)
You responded within the first day, which is already fast. The shorter the time they give to schedule (Late Monday sent, Thursday to schedule), the more reasonable it is to having a reschedule due to timing problems from one of the sides.