My kids try that, “It’s still light!” shtick on me in the summer here. Doesn’t work. Bedtime is when I say it is.
You may think bedtime is when it’s too dark to do anything fun.
You may think bedtime is when you’re too tired to do anything fun.
But bedtime is when I tie you in bed so I can do stuff without you. Now quit squirming.
My daughter had a problem with getting up when it was light when we moved to Olympia. So I got her up and made her stay up and no naps during the day. A couple of days of this and she was more than happy to stay in bed and sleep!
And yes — bedtime is when you say it is!