@ OP - I'd say all day on the weekends and/or days off is acceptable -IF- you're NOT leaving the house or going to see anyone face to face. What people do in their own home is largely on them, but even if I'm in my PJs all day, I still put on a shirt and real pants or shorts (I live in LA, too hot to wear jeans/pants right now) to go outside and walk to my mailbox.
I would NEVER run to the grocery store in PJs. Even if I was sick. I don't even really go to the grocery store or in public if I haven't showered (unless I showered the night before).
In public, I cannot understand PJs at all. This really got on my nerves the last few times I've been flying somewhere. WTF people? The airport and airplanes are public spaces! They are not your hotel room! It's fine to dress comfy for a long flight, wear yoga pants if you're a girl, or slip on shoes like Vans or non-skinny jeans if you're a guy... but grow the fuck up and wear real clothes in public!
This goes to celebrities too! In fact, I think they started the trend in the last 8 years of wearing PJs in the fucking airport! I get that most celebs are sleep deprived and jet lagged all the time but the airports lately are full of assholes who think it's OK to wear PJs in public because they see celebrities do it.
If restaurants can have dress codes, then fucking airports and planes can too. We don't need to get in the 1960's mindset where we wear our best clothes to travel but fuck, flying is not a utility nor is it a right, it's a privilege granted by private companies. Show a little dignity and self-respect in the airport.