Due date

Stacy
Obviously Glow gives an estimated due date based on your last period. I'm wondering how accurate that date was once you went to your first doctors appointment. 
I'm pregnant with my second child, but it's been 10 years since I was pregnant last so I don't remember everything lol.
Update: I had my appointment on Friday and I'm measuring only one day off from the GLOW predicted date. My due date is now January 16, 2016.