How long can a baby be away from mom?

In another thread a bride was called a bridezilla for not wanting her bridesmaid to bring her 5 month old to a child-free wedding. The comments included “Clearly this bride is not a mom because she doesn’t understand that not all babies can be left for that long a period of time.”

I don’t want to threadjack that thread, but I’m wondering – is this true? My understanding is that after a few months (or even a bit sooner), a baby can definitely be left with a trustworthy caretaker. My mom only had 2 months of maternity leave and then was working full time, so she was leaving me for 8+ hours after that. 

I obviously recognize that newborn infants can’t be left for long. And that breastfeeding adds a difficult element. But do a lot of women feel like they can’t be away from their babies for a few hours for 5+ months after they’re born?