Advice on effects of dawn simulator

Hi, I'm new to this so apologies for the ignorant question - if I wake up at 6.45 / 7am in winter, with the aid of a dawn simulator, does it mean that I'm going to be shattered come 4pm when it's dark again?? I'm thinking about buying one of these as I struggle to wake up in the darkness (I'm also very sensitive to light and struggle to sleep once dawn breaks in the lighter months) but am curious as to the effect. Also, assuming I were to set it early enough that I'd also leave the house whilst it was dark outside, would my body be very confused by the "dawn" which actually isn't real? These questions do sound a bit odd even as I'm typing, so I hope someone understands what I'm asking! Thanks...

Thank you Paul.
Are you able to tell me what is the "white noise setting" on the advanced Bodyclock? I'm trying to choose between this and the standard version.
Thanks!

It makes a noise rather like the old noise when a tele is inbetween stations.

It is supposed to help you get to sleep, one way or another - it supposed to work on babies too. Cancels out any other noises from other sources.

However, I always found I was still awake when it faded, so doesnt work for me.

Supposed to be good though.

I like the sunset setting on my dawn simulator!

I use the sunset option every night,it really does help me relax. Sorry rosie, I know very little about other brands.