HeadsUpDaddyHow it works
Cycle logging → prediction → the DEFCON ladder
Four moving parts, all running on your phone: what you log, what the app predicts from it, how that prediction becomes a threat level, and what actually gets sent to your lock screen.
Step 1
You log two dates. That's it.
Started / Ended
Two buttons, always on screen, a date picker defaulting to today. Logging takes under five seconds.
The day-of check-in confirms it for you
On the predicted start date, a notification asks “did it start today?” Yes, No, or Remind me tomorrow — all three work straight from the notification, no need to open the app.
History stays editable
Fix a date, add a period you forgot to log, or delete an entry. Any change immediately recalculates every prediction and reschedules every notification for that profile.
Step 2
The prediction is honest about what it doesn't know
Built from your history
Average cycle length comes from the last several logged cycles, with one-off outliers (a missed log, a 50-day gap) automatically excluded so a single bad month doesn't poison every future guess.
Three confidence states
High confidence runs the normal ladder. Low confidence widens the warning window and delays nagging you about a missed period. No usable history yet gets a flat estimate, clearly labelled as one.
Calendar days, not timestamps
Cycle dates are stored as plain calendar days, so a flight across time zones never silently shifts a prediction by a day.
Step 3
The DEFCON ladder
Six threat levels, derived fresh each day from the prediction. The number and the label are always shown together — colour is never the only signal, and under low confidence the dial gets a visible hatched treatment plus the word “estimate” rather than a false-precise number.
| Level | Label | Window | The read |
|---|---|---|---|
| 5 | All clear | Follicular phase | Be a person again. |
| 4 | Green light | Fertile window (partner profiles only) | — |
| 3 | Situation developing | Early luteal, ~T-13 to T-8 | — |
| 2 | Shields up | PMS window, T-5 to T-3 default | — |
| 1 | Maximum threat | Final 48 hours before onset | Say nothing. |
| ON DUTY | Contact | Logged bleeding days | Heating pad deployed. |
For daughter and “other” profiles, level 4 doesn't exist — there's no fertile-window concept to surface at all — and every label uses the same neutral, Plain-tier vocabulary. There's no joke mode for a daughter's biology.
Why it starts at T-13
Luteal shift → PMS window → peak difficulty
Luteal shift, ~day 13 out
The easy half of the cycle ends. Nothing dramatic yet — this is a heads-up that the runway is starting, not an alarm.
PMS window opens, T-5 to T-3 by default
A single T-3 warning fires after this stretch has already begun. HeadsUpDaddy's DEFCON 2 notification lands right as the window opens instead.
Peak difficulty, final 48 hours
DEFCON 1. The hardest stretch, and the shortest one. The app's advice narrows to the one thing that actually helps: less talking.
How early each rung fires is set by a severity question asked once per profile — mild, noticeable, or rough — and every notification type stays individually overridable afterward.
Step 4
18 notification types. You don't need to touch most of them.
A conservative set ships on by default; everything else is opt-in per profile.
Pre-window heads-up
Default on. Fires a few days before the predicted start.
Day-of confirmation
Default on. The actionable one — confirming or correcting it is how predictions stay accurate over time.
All clear
Default on. Fires when the period ends, or is estimated to.
Missed-prediction nudge
Default on. Stays flat and joke-free in every tone — this is the app admitting it might be wrong, not a punchline.
PMS window opens
Default on. The DEFCON 2 transition — the notification this whole app exists to send on time.
Fertile window & peak fertility
Off by default, partner profiles only. Structurally unavailable on daughter and “other” profiles — not hidden, not present at all.
Also included: supply-check and gesture-suggestion reminders, mid-period check-ins, a monthly pattern note, planning guard, survival streak, and a mission debrief — each individually toggled, timed, and quiet-hours aware per profile.
Please read this part
HeadsUpDaddy is not medical advice. It is not a contraceptive and must never be used as one. It is not a fertility treatment. It predicts a calendar, not biology you can rely on for anything medical — talk to an actual clinician for that.
See how consent works
HeadsUpDaddy is built to be handed to the person it's about, not hidden from her.
Read Yes, She Knows