I'm how far along??

So I had quite the experience when I called to schedule the 20-week ultrasound...

From the first appointment I had, the timing worked out that the weeks "started" on Thursdays...which would make one think week 20 would start on Thursday, Oct 22, right? So I had Steve's schedule for that week, and called, ready to go in almost any time. Then the girl told me it'd have to be exactly week 20 or later...and according to her "dating wheel," week 20 started on Oct 24. Now wouldn't you think that the same wheel would be used throughout the clinics and labs? I did. So I had to talk to Steve to get his schedule for the next week...and then called back. This lady told me that she was in "the back" so she didn't have the same wheel as the people at the front desk... Really?? Is it square? Her wheel said that week 20 was Oct 26! So, that's when it was booked... *sigh* Not a big deal, but you'd think that 3 people using the same "technique" would be able to tell me i'm the same number of weeks along - right? Amazingly enough, they all said I had the same due date... Oh well...the baby will be here when it's ready :)