So your manager said please and reminded you of your working hour commitment. I don't see any harm there. I get your point that 5-15 minutes late is really ki

So your manager said please and reminded you of your working hour commitment. I don't see any harm there. I get your point that 5-15 minutes late is really kind of nitpicking, but you mention the company has traders and risk managers, which makes me think you are in financial industry or maybe commodities. For those guys they will pay you to be sitting there watching youtube as long as you are there to respond when they need you immediately. And for them if trading starts at 9 and stuff is broken at 8 when they are getting setup that is major and so they want people in the seat ready to fix it, not wondering when you are going to stroll in. That frankly seems reasonable to me. At the same time you'll have the benefit of a pretty easy job and a 5pm quitting time that will be firm as well. So really it is up to you, but I would say you need to have some accountability and the excuse you aren't a morning person won't cut it in standard corporations. If you want flex time, find a new employer that specifically allows for that and you'll be good. * edit: added a word