I have been using Flo for six months. When I first opened it, I sat down and logged a year and a half of old periods from memory. Guesswork, mostly. Old chat threads. Screenshots. Photos whose timestamps did most of the remembering for me.

I didn't think anything would come of it. It felt like the kind of task you do once and forget, like filling in an emergency contact on a form nobody reads.

Then, a few months in, it started being right.

The App Started Knowing Things First

Woman checking phone screen early in the morning

Not just the period. That part I expected.

It started telling me things about the week around it too. Low energy expected. Mood may dip. And I would roll my eyes and close the app and go about my day like it hadn't said anything.

Then by Wednesday I would be lying on my bed at 4pm with the lights off, not sad exactly, just unavailable, and I'd remember the little notification from Monday.

A calendar tells you where you'll be.
It took me a while to notice Flo was telling me who I'd probably be when I got there.

My Jeans Started It, Actually

Pair of jeans lying folded on a bed

This is the part I keep coming back to.

My favorite jeans suddenly felt uncomfortable. Nothing had happened to them. Something had happened to me.

I checked Flo out of habit more than concern. Day 24. Progesterone rising, it said, in that clinical little font apps use to sound trustworthy. I didn't fully know what that meant. I just knew my jeans suddenly felt like they belonged to someone else.

That's really where this whole thing started. Not with a period. With a pair of jeans I almost gave away.

The Science, Briefly, Because It Explains the Jeans

Simple illustration representing hormonal cycle phases

Here's the short version. I mean actually short.

Estrogen rises in the first half of the cycle and tends to bring energy and clarity, a kind of social ease. Then Progesterone steps in. Things slow down a little. Sometimes that's your energy. Sometimes it's your patience. Water retention. Lower mood. Less patience for group chats.

That's it. Two words, one sentence each, and suddenly the jeans made sense. So did the Wednesday at 4pm.

Nobody mentions the jeans in school. They explain the biology. Nobody explains what Tuesday afternoon feels like. They give you a diagram of ovulation and call it done.

What Flo Is Actually Naming Each Week

Calendar showing the four phases of a menstrual cycle

Once I actually understood what the app was tracking, half of my "for no reason" days stopped feeling like they had no reason. So here is the plain version, the one I wish someone had explained to me earlier.

Menstrual Phase
Days 1 to about 5, though it varies for everyone. This is the period itself, the first day counts as day one of the whole cycle. Estrogen and progesterone are both at their lowest here, which is part of why energy dips and some people feel low or slow. Your body is shedding the lining it built up the month before. Rest actually helps here more than pushing through does.

Minimal illustration of the uterus representing the menstrual phase of the menstrual cycle

Follicular Phase
This technically starts on day one too, alongside the period, and runs until ovulation, so it overlaps with the end of the menstrual phase before continuing on its own. Somewhere after the bleeding stops, estrogen starts climbing steadily. This is the phase where your body is preparing an egg to be released. As estrogen rises, most people notice better focus, more patience, and a kind of returning energy. This is usually when replying to messages stops feeling like a chore.

Illustration of a woman using a period tracker during the follicular phase of the menstrual cycle

Ovulating Phase
A short window, usually just a day or two, right in the middle of the cycle, around day 14 for a fairly average 28 day cycle. Estrogen peaks here, and this is when the egg is actually released. A lot of people feel their most confident and social right around this point. It is often the easiest time to say yes to plans without overthinking them.

Illustration representing ovulation with a confident woman and a highlighted ovary releasing an egg

Luteal Phase
The longest stretch, roughly two weeks, from right after ovulation until the next period starts. This is where progesterone takes the lead. If the egg was not fertilised, progesterone eventually drops toward the end of this phase, and that drop is what triggers the next period. This is also the phase most associated with bloating, cravings, lower energy, and shorter patience, especially in its final days. Some people barely notice a shift here. Others feel it clearly.

Editorial illustration showing the emotional shift and lower energy often experienced during the luteal phase

None of this fits everyone exactly the same way. Cycle length, stress, sleep, medication, and plenty of other things change how each phase actually feels. The point was never to match a chart perfectly. It was just to finally have a name for what my body was already doing every month.

The Week I Say Yes to Everything

Woman confidently enjoying an active and productive day

There's a stretch every month, usually right around ovulation, when everything feels lighter. I want to see people. I finish things I've been putting off for a week. I'll try an outfit I would have talked myself out of on any other day.

Those became the days I started scheduling the things that matter. Meetings I actually wanted to be sharp for. Trips. Photos, even, because I genuinely liked how I looked in them.

It wasn't about forcing productivity. I just learned which days my body was already offering it.

Some Weeks Are Just Different Weeks

Calendar and planner on a desk beside a coffee cup

I used to think I was inconsistent. Some weeks I'd reply to every message within the hour. Other weeks I'd leave someone on read for two days and feel nothing about it. Not even guilt. Just distance.

I thought that made me flaky. Maybe I wasn't.

I only noticed the pattern because Flo kept naming it before I did. A quiet flag next to certain dates. I'd look back later and think, oh. That was always going to be a heavy week. I just didn't know it yet.

Now I Check It Before I Book Anything

Hand holding a phone while booking train tickets

This is the part that surprises people when I say it out loud.

Before I book train tickets, I check Flo. Before a trip. Before a big dinner. Before deciding whether to wear white trousers somewhere I can't easily leave.

Not because I'm scared of my body. Because I've stopped pretending my body doesn't have a say in my week.

A calendar only tells you the date.
It has never once told me how I'd feel showing up to it.

Flo does. Or close enough to count.

I still bought pads twice last month despite the little pink icon sitting right there on my home screen telling me exactly when I'd need them. Old habits don't leave just because a new one shows up. They just sit next to each other, a bit awkwardly, like two friends who don't really get along.

What I Think Is Actually Happening Here

Woman sitting quietly by a window looking outside

I don't think this is really about periods.

I think it's about spending most of your twenties assuming you're the same person every day, just placed in different situations. Different meetings. Different outfits. Same self underneath, showing up consistently.

And then an app you downloaded for a completely unrelated reason quietly tells you that isn't true.

There's a version of you that wants to talk to everyone. A version that wants silence and a closed door. A version that will cry at an ad for no clear reason and then be completely fine an hour later.

The app didn't create these versions. It just started naming the days they show up.

Closing Thought

I don't know what I did before this. Blamed myself, probably. For cancelling plans. For the jeans.

Now I just open the app, see the little note next to the date, and think, ah. That's who's showing up this week.

And then I get on with it.