Up until what time (how late) is it okay to use a lawn mower in a residential area?

I need to cut my grass and can usually do it around 7-9pm.

I'm just wondering, how late is too late to be using a lawn mower In a residential area? I don't want the neighbors mad at me for making noise.

What do you think? Is 9pm the time to stop?
Update: City by-laws say no noise after 11pm. So I won't go by that. Lol. But just wondering what everyone else thinks. How late is too late?
Update 2: Thanks everyone. I guess during daylight hours is a good gage to go by. My lawnmower does have lights but I don't need to use it at night.
Also, thanks for mentioning that kids got to bed early. My lawnmower is battery powered, so it's not THAT noisy.
10 answers 10