If you own a microneedling pen, a red light mask or a radiofrequency device, using it is the easy part. Knowing when is harder. How long since the last session, what shouldn't follow what, and whether your skin has had its recovery days.

Regimen is a skincare planner for at-home devices and the actives around them. Tell it what you own and what you're working on. It builds a repeating schedule, keeps every session spaced, times each one and tracks what you did.

SEVEN DAYS TO TRY, THEN ONE PURCHASE
Your first seven days are free, from the day you build your routine. Every feature works in that week. After that, Regimen is a one-time purchase through Google Play. There's no subscription. If you don't buy, nothing is deleted. You can still export your data and see when each device is next clear.

BUILT FROM YOUR OWN KIT
Pick from 21 kinds of device: derma rollers, microneedling pens, light-emitting diode (LED) masks, radiofrequency, microcurrent, intense pulsed light (IPL) and more. Add products from 39 kinds, from retinol and vitamin C to exfoliating acids and sunscreen. Products alone are enough to start. The cycle runs 7 to 28 days, starting the day you build it. Reminders follow the schedule, and every step stays editable.

SPACING FOR EVERY DEVICE
Each device and active has its own minimum gap and conflicts. A retinoid and an acid never share a night, and actives rest after needling. Two needling depths take turns, at least a week apart. If a session comes too soon, Today says which session is holding it and when it opens. The call is still yours. Flag flaking or redness and the cycle adds recovery days after the heaviest sessions. After sessions that leave skin sun-sensitive, Today shows your area's ultraviolet (UV) index.

A WEEK BUILT AROUND YOUR RETINOID
Retinoid nights, exfoliating nights and recovery nights each get their place in the cycle, the rotation people call skin cycling. Choose Retinoid nights first and your retinoid keeps three nights in seven ahead of devices. A new retinoid ramps up at its own pace, and Today says this week's amount.

GUIDED SESSIONS
A full-screen timer takes each session zone by zone. Spoken cues and voice commands are there if you want them, so the phone can stay on the counter.

PROGRESS PHOTOS THAT LINE UP
An oval, an eye line and a level readout keep every shot at the same angle. Compare and Replay line photos up by the pupils, found on the phone itself. Each photo remembers which routine was running when it was taken.

SEE WHAT YOU ACTUALLY DID
Progress shows the steps you kept, by device, over 30 days, 90 days or all time. A session the spacing rules held back doesn't count as missed. A skin load gauge compares your last 7 days with your average week.

PLANS AROUND YOUR LIFE
Plan back from a date and see the last day for each device. Enter a clinic procedure and actives step aside before it, then ease back in after it. Pause a device, mark a product as run out, take a longer break, or let the schedule follow your hormonal cycle.

WHO IT'S FOR
People using at-home devices, actives such as retinoids and acids, or both, who want the timing handled. If your routine is cleanser, cream and sunscreen, this is more app than you need. It sells nothing and works with what you already own.

PRIVATE BY DESIGN
No account and no ads. Your log, routine and photos stay on your phone. Not even Google's backup gets a copy, so keep your own backup file. The app works offline. It goes online for the sun forecast if you turn it on, by rounded location or a city you pick. Until you buy, it also checks Google Play for a purchase.

NOT MEDICAL ADVICE
Regimen records cosmetic sessions you choose to perform and tracks the intervals between them. It does not diagnose or treat any condition, and it is not a substitute for advice from a dermatologist or other qualified healthcare professional. Follow the manual supplied with each device.