When do camp slots go on sale? Rough dates?

Recently been playing fallout 76 again, past 2 months I have been really into it so I started a new character did all the quests etc. And loved all the new stuff and the new events and seasons but I always see people say they put camp slots on sale about 2times a year? Even searching i cant find more info than that

Back when I first played on release you could only have 1 camp so I had so many characters to build new things 😂 but now having multiple on one character would be amazing but im wondering when roughly these 2 sales are? Really want to make a new build but id like to pick up a sale if possible and hate to buy one and then the sale pop up soon when I could of waited