Re: Time of day?
Don't forget -- babies nap during the day after nursing so that wouldn't make sense for something to be in the milk that would keep them awake. Anything you pump in the day would be the same as the milk you'd nurse with. My LO fell asleep on the same schedule for our sitter with bottles as she did with me nursing -- the bottles at nap time during the week knocked her out as well as nursing did on the weekends.
Mom to my sweet little "Pooper," born 10/12/11, and "Baby Brother," born 6/23/2014, and married to heavy metal husband. Working more than full-time, making healthy vegetarian meals for family, and trying to keep up with exercise routine.