[Always *]

See it depends. I won't necessarily tell them (read: mostly my dad) that I am on a date or something, like they don't need to know. I used to have a thing with a guy (read: we are friends but we used to have sex) and I would talk to my mom about him BUT only as him being my friend, I never told her about the errr... extra benefits lmao... though she may have guessed as much... i had all of 2 boyfriends in high school and my parents new about both. I didn't tell them instantaneously, but it was within a reasonable amount of time. But my parents are not the kind of parents to be nosy about things. I am sure if they REALLY hated a guy (like if he was an insane violent criminal or what ever) then they'd maybe speak up but I wouldn't be dating a psychotic criminal to start with so it'd never be an issue.
Now I am an adult and don't live at home so my parents can't really do anything about it. Things like if I went on a date or was hanging out with a male friend wouldn't need to be clarified for my parents because they are not here to see it (plus they're smart enough to know my friends from my dates). So if I was "seeing" guy I might mention I'd like just met a guy and we were hanging out... But I'd use well chosen language (ex. we are "hanging out" not "dating" that way my parents won't feel bad or what ever if it doesn't work out. If it ever became a real relationship, yeah I'd tell my parents, but maybe within a few weeks. I have never felt like it needs to happen the day of (unless it just happens that way). But like I said my parents aren't going to nose in unnecessarily.