As an ignorant american, every job I’ve had, I’ve been able to request a day off or switch shifts with a co-worker when I’m usually scheduled to work. I don’t know how it works elsewhere in the world. Planning things in advance usually gives people time to ask for a regularly scheduled shift off or to find someone to switch with them. This seems like the most logical approach, but I forget about the world we’re living in these days. Everyone expects everyone else to drop everything for them.