Here's a thorough walkthrough of everything Duonidus can do, with concrete examples along the way. Jump straight to a section using the list below, or just read straight through.
Create an account, then invite the other parent to join your shared calendar. You both need to be signed up before the calendar can be used to split days between you — until then, you'll see an invite link you can pass along.
Every date in the calendar is split into two halves: a morning half and an afternoon half, so a mid-day handover can be agreed on precisely. Click an unclaimed half to claim it — it immediately turns your color. Click it again to release it. How wide each half looks is up to you, under Display settings.
How to read the calendar
Want to take over a day the other parent already has? Double-click it, and a request is sent for them to approve. Want to give up a day you have to them instead? Double-click it (in a locked month) to offer it. If a half isn't claimed by anyone yet, you can instead long-press it to open the note dialog and click “Offer this day to the other parent” — offering it to them directly, bypassing the usual request dialog. That half then gets a bold border in the other parent's color, shaped like a C pointing toward the adjacent date, since the two halves are really one continuous period. When the other parent logs in, they won't be interrupted by a pop-up — they need to long-press the day themselves and click “Accept the takeover of this day” in the note dialog. When a dialog pops up asking you to confirm a takeover, you can drag it out of the way by holding the move icon in its corner, so you can still see the calendar behind it.
Experiment freely below — nothing is saved, so you can't get it wrong. Use Previous/Next to step through the four stages.
Long-press any date to write a note on it — handy for handover details, birthdays, or anything else worth remembering. With a paid add-on, you can also give each note a colored category, so things like “school” and “activities” stand out at a glance in the calendar. Tap 🔁 “Repeat note” in the note dialog to make the note recur every week or every 2 weeks until a chosen end date (e.g. “Swimming”). If you later edit or delete a repeating note, you are asked whether it applies to that note only or to all following ones too.
Once you've agreed on a month's split, either of you can propose locking it. The other needs to approve the lock, after which days in that month can no longer be claimed or released with a single click — only through requests, offers, or direct offers to each other. This prevents accidental changes once the plan is set.
Under “Planning” you can set up a repeating 14-day pattern (e.g. “a week with each”) and apply it over an entire period at once, instead of clicking every day by hand. There's a matching note pattern too, so recurring notes (e.g. “swimming every Tuesday”) can be set up for a period as well. If applying it conflicts with days already claimed, you can choose to skip those days or cancel the whole application.
You choose how wide the morning and afternoon halves appear in your own calendar view: “Full day” shows the whole field as one color based on who has the evening, “25/75” makes the morning half narrower, and “50/50” (default) splits it evenly. This setting is personal — it only affects your own view, not the other parent's.
There are 17 color themes to choose from. Under “My profile” you pick exactly 3, which then become the ones you can quickly switch between in the calendar itself. With a paid add-on, you can also use the dice button to have a random theme picked from all 17.
The statistics page shows how many days each of you has had — in total, per year, and per month — so you can easily keep track of whether the split is what you intended.
Under “Communication” you'll find a shared chat, a handover checklist, and a shared note you can both edit — handy for arrangements that don't belong on a specific date.
You can create a read-only link that, say, grandparents can use to follow the calendar without being able to change anything. You'll find and manage the link under “My profile”.
With a paid add-on, you can subscribe to a personal calendar feed (ICS) that keeps your phone's own calendar app updated automatically, or import from Google Calendar. The feed link is personal and shouldn't be shared.
Most of Duonidus is free. A paid add-on unlocks extra color themes beyond the 3 basic ones, note categories, calendar sync and phone notifications. The subscription is handled via PayPal and can be cancelled at any time under “My profile”.
Under “My profile” you can change your language, change your password, and see an activity log of changes made in the calendar. Under “Privacy” you can download a full export of your data or read how it's used.
Duonidus can notify you on your phone when the other parent asks to take over a day, wants to give a day to you, or offers you an unclaimed day. Every evening at 9 pm you also get a short reminder if there are unanswered requests from the other parent or unread messages in the chat — if nothing is outstanding, nothing is sent. Notifications are part of the paid add-on and are turned on separately for each device under “My profile”.
How to turn them on on an iPhone
Notifications not showing up?
On Android and computers, notifications work directly in the browser (e.g. Chrome, Edge or Firefox) — just turn them on under “My profile”.