Given my current schedule (including work) I am often up very late at night. I am looking for a new job and was wondering, does it look bad if a employer receives an application form at 3am or sometime where most people are sleeping? I am looking for more regular jobs (around 9-6) and expect to have to adjust my sleep schedule and am prepared for this.
Short answer: no.
The hiring manager will come in the next morning, have 3 new applications and won't care enough to look up the time-stamp when exactly they came in.
If you are in current employment you might have no opportunity to apply for other roles during the working day, so applying for jobs at night is pretty much what most people have to do.
For companies who perceive this as negative, they would have to make assumptions as to why you applied late at night, and if they do that then you should ask yourself do you really want to work for them?
You will find that most don't even look at the time in which an application was received, a lot of HR departments deal with printed CV and cover letters and will never even know when you applied for a job. Smaller companies might know, but are unlikely to care.
The biggest factor in terms of when to apply for a role should be making sure you apply for the role as soon as possible.
There are at least 10 reasons that I can imagine for why you would apply late at night, and none of them would be of any interest whatsoever to me as an employer.
I'd hazard a guess that the majority of the employers doesn't even look beyond the date portion of the timestamp, at all.
No. few people, if any, look at the timestamp of an application. I don't. Even if I did I would simply assume that you were employing a tactic to submit as late as possible to be the first application I saw when I got in, so if anything I would think you were either clever or using every available moment to job hunt.
Generally I agree with what Agent L and Jonathon Cowley-Thom have said. Given that so many hiring managers are inundated with applications nowadays, I doubt they'd have the energy to consider the time you applied. Depending on what kind of electronic application system the employer is using, they may not even be able to see the time that you applied. In general I think it would take a lot for a hiring manager to consider that.
I'd also like to point out that when it comes to federal jobs, they're almost all posted on the USAjobs.gov website. While some are posted at various times throughout the day, most are posted at midnight when their system updates. I consider myself a very well versed applicant, and I'm very motivated about my career. So depending on my schedule, I often stay up late into the night, or get up very early in the morning to check what jobs have posted. Especially considering that many of the more desirable jobs will close after receiving a set # of applications. The system is automated and my resume/transcripts/certifications are all uploaded, so I have applying down to a matter of minutes.