The 3am clock

 I'm starting to catch on with a pattern here. Every night my Georgia wakes up at 3am sharp and is back asleep by 3:15-3:20.

It has nothing to do with when I put her to bed..her normal bed time is 9pm and tonight it was 11pm. She also has nothing against time zone changes-still wakes up at 3am. We live PST and are in MST now- both places 3am

This is the second night I have actually stayed up past her 3am mark... I start to hear her rustle in bed about 2:50 and then DING DING 3am and she is crying for a feeding.

I find it very strange... How does she know it's 3am?