The interviewer didn't contact me when they said they would. Is this a bad sign?

Hi all,

I had a first-round interview on Wednesday for an analyst role with a company I really admire.

I did a lot of preparation for the interview - researching the company, networking with employees and former employees, researching industry news, looking at the company's case studies, and tailoring my interview answers to match the keywords and skills in the job description.

I went into the interview full of confidence, excitement and energy. I wore a shirt and tie and had a smile on my face. The interview lasted around 35 minutes. I made the interviewer laugh a few times; they said they liked my answers to their questions because they were well-detailed and comprehensive. I showcased my research of the company, company news and case studies. I asked 4 questions at the end (I wanted to ask more but the interviewer said they had to go). They were impressed by 2 of the questions I asked and were taken aback by my final one as they said they hadn't heard that one before, and he said it was very insightful. The whole vibe of the interview seemed great, we got along well and shared common interests.

Before signing off, the interviewer said the first-round interviews were being concluded later that day (Wednesday) and that I should hear back either Wednesday afternoon or Thursday (yesterday).

Well, yesterday has passed and I haven't heard anything.Is not hearing back when he said he would contact me a bad sign?

I heard from a few people that interviewers/recruiters contact successful candidates in the morning and then send the rejection emails in the afternoon or they'll contact the successful candidates on one day (Thursday) and then the unsuccessful ones the following day (Friday/today). Is this true?