It could be the pharmacy, because what you're explaining is exactly how it used to work for me. It depended on how many days in the month there were as to when the new script was filled for me.
My doctor always prescribed mine on the same day every month...which for me was the 19th. If that fell on a Saturday or Sunday, they moved it to the 20th or the 21st. I guess they expected me to pace myself for those days...and I was able to do that.....but, I honestly don't know how other doctors
handle that. And once they moved it to the 20th, they changed that to the day that I came in. They never let me come in a day or so early. But, again, I don't know how other doctors do that. Hopefully, someone will come along and say.