I started at ten too.
OTR (on the rag), got the Dot, flying the red flag.
I haven’t heard “falling off the roof” in decades. I never did get it.
We called them “M” days in high school, too. That’s because the gym teacher would mark us as an “M” in her book when we didn’t have to take a shower due to our period. We were all “M” all the time. I think they finally started storing basketballs in the girls shower.
A fabulous one I heard from a British friend was:
“Having the builders and painters in.”
I don’t know the origins, exactly, but I liked it.
On the blob.
The crimson tide.
the red tide.
Used by a phlebotomist I used to work with re: her daughter’s mood: “She’s out of sorts because she’s comin’ on.” Or when dealing with an uncomfortable female patient: “She said she felt like she was about to come on.”
Being a medically-oriented type, menstruation was never a big deal with me. It’s just another bodily function, only more annoying than the rest (I’m a guy, BTW, so take that POV with a grain of salt). My daughter started when she was about 10, and was mortified at first (about the whole blood thing, and then about my blase attitude). Now she mentions it casually at the dinner table if her period is relevant to the discussion at hand or when mentioning her mood. If she and I are shopping, I’ll sometimes ask if she needs “feminine hygiene products.” At 17, she just started using tampons, after years of pads and black underwear.
SeaDragonTattoo’s comment about Dad getting a zit at that time of the month is curious. Before my wife hit menopause, I used to get really, really (annoyingly) horny a few days before her period started. I don’t notice that anymore, and feel like I’m on a more even keel. Marlitharn’s comment about mortifying her father is also funny. I’m a medical technologist, and you can’t mortify us. Never, never eat dinner with us unless you have a strong stomach. 
Vlad/Igor
Having the painters in.
So if you’re a female Alabama fan, you roll tide? 
Robin
Shark week. (Blood in the water)
I also occasionally call “feminine hygiene products” a “chartreuse flamethrower”, after a Bloom County comic strip in which the characters misinterpreted the meaning of what “feminine protection” could be.
Red-letter day. I used RLD on my calendar for many years to note the first day of my period.
From my recall it’s just ‘having the painters in’ and it’s use is more a way of saying ‘normal service will soon be resumed’, than a descriptor of the actual process. imo.
I used to wonder why Alabama had a football team that may as well have been named The Alabama Menstruators.
One I heard when I lived in Rochdale.
Vampire Soup
Good God , people, I know you wanted dumb ass euphemisms, but y’all are gonn a scare little Marli.
Tell her it’s a booboo foofoo and she’s a special kind of bear.
The moon is full (from Stephen King’s “Rose Madder”).
Time of the flower.
Mine sucked because I had no idea what it was. I hadn’t read anything about it or had any sort of talk with my mom about the birds and the bees at that point. Also I got as sick as a dog my first time and had been hiding it from my parents. I was so embarrassed when my mom found out I didn’t want her telling my dad. Plus the fact that I had to start wearing a bra in third grade, it didn’t pan out well for me.
I got my first period the month I turned 11, so once my daughter turned 10 I explained the whole process, showed her how to use a pad, and made sure she always had some in her backpack, in case she was at school when it started.
As a result, she was so well-prepared and blase about it that she didn’t even tell me when it happened. 
Not that I’d change anything, but it would have been nice to have that commemorative shopping and ice cream day.
It’s just us, so we’re not really about the euphemisms. It’s always just been “I have my period”. Except when we’re inordinately cranky about it for some reason, in which case it’s more “I’m bleeding out my f*$@#n vag again”.
I was 11. My mother had never told me anything, but somehow I knew what a period was. When I found a small spot of blood in my underwear, I went in her room and told her, “I think I’ve started my period.” She calmly and matter-of-factly replied, “That’s entirely possible. Let me see your underwear.”
Well, given that she’d never even discussed it with me, she was totally unprepared. All she had were tampons, which she was unsure about having an 11 year old use, and pads. But remember we’re talking about 36 years ago; pads didn’t come in maxi and mini and liners and such, it was one-size-fits-all-jumbo. And there were no such thing as sticky strips; they had long, extended ends that were wrapped around a hook that hung from the front and back of a belt you had to wear around your waist! She gave this contraption to me to wear, as I was getting ready to go to ballet class, wearing a leotard and tights! :eek:
Thankfully she called her doctor the next day and asked how early to have me start using tampons and he advised her to have me get used to them right away (Og bless him!).
Woman, you never cease to crack me the heck up! 
Congrats to Mini-Marli! BTW, she might enjoy this book.
Oh god, the belt! The belt and the brontosauruspad that actually covered the majority of my tiny eleven year old lower torso. Thank god it was only for one night, but it was all my mom had in the house, left over from when she’d had my brother a few months earlier.
Thank you! Yeah, we’re really not very delicate around here. The last time I was complaining about cramps, my daughter said “You know, it’s not like you’re **using **that thing for anything. If you had any other body part that only ever hurt and bled, they’d suggest you get rid of it, right?”
Geez, I had forgotten all about the belts. I don’t remember when they came out with the sticky strips and different sizes. The old style only came in one size - gigantic - and could be seen under anything that you wore from 50 yards away. I was forbidden to use tampons until high school when she couldn’t stop us from getting at the machines. I think that my mother had somehow linked tampons with losing your virginity.
One of the things that I love about my partner is that he’s not only willing to run to the store for me, he wasn’t the least bit embarrassed when he broke his nose on a trip, reset it himself and then stuffed 2 tampons in it to stop the bleeding. I would have given anything for a camera at that moment.