PMS calculator: see when your hard days start

PMS usually starts 5 to 7 days before your period and eases within a day or two of bleeding. It sits in the second half of the luteal phase, after progesterone peaks and starts to fall. With PMDD, symptoms can start earlier, sometimes right after ovulation, about 14 days before your period.

Your own window depends on your cycle. If your cycle is 32 days, your PMS lands later in the month than someone with a 26-day cycle. That’s why the calculator asks for your length rather than assuming 28.

It is as accurate as your cycle is regular. The luteal phase, from ovulation to your period, is fairly steady at 12 to 14 days for most people. The first half of the cycle is the part that varies. If your cycles swing by more than a few days, treat the window as a heads-up, not a date.

Logging two or three cycles makes it much sharper. Niyora learns your own rhythm from your period history or Apple Health and predicts your PMS window from your cycles, not an average.

Knowing the dates is useful only if you do something with them.

• Move what you can. Big conversations, hard deadlines and difficult visits go better outside the window.
• Tell one person. A partner or friend who knows the dates can read a rough evening differently.
• Plan the moment, not the week. The hard part is usually a single message, argument or 3am spiral. Decide now what you’ll do when it comes: twenty minutes before replying, a walk, a breath.