Day by Day was built for my wife, Hazel, while she is undergoing chemotherapy for breast cancer. It started as a simple request: "Can you make me a spreadsheet to track my medications?"
The spreadsheet worked – but it wasn't the right shape for real life. We needed something that was always to hand, mobile-first, and quick to update as medications were taken. So I took the spreadsheet idea one step further and built Day by Day as a small, calm web app.
Day by Day is for anyone going through treatment (or supporting someone who is) who needs a simple way to stay on top of a busy day – without turning life into a full-time admin job.
The goal is not "more features". The goal is less stress. If something adds friction, confusion, or clutter, it probably doesn't belong.
No accounts. No sign-in. No syncing. No server. Your data stays on your device and remains yours.
This isn't trying to be a medical system. It's meant to be quietly supportive: reminders, a record of the day, and quick access to useful information and contacts.
Day by Day is a self-contained web app designed for a phone screen first. You can add it to your home screen and use it like an app.
Day by Day stores data locally in your browser on your device. There is no backend and no account system, so nothing is uploaded by default.
If you choose to email a daily summary, that email is sent using your own email app and settings. You are in control of what is shared and with whom.
Day by Day was developed by Ken McCarthy. Generative AI tools – Claude and ChatGPT – were used during development to help draft, refine, and iterate the HTML, CSS, JavaScript, and interaction patterns based on prompt-driven instructions.
The app uses the following open-source libraries and external services:
The navigation icons follow the Heroicons style (heroicons.com).
The aim was to use these tools as practical accelerators, while keeping the intent, design choices, and responsibility for the app firmly human.
Day by Day does not provide medical advice, diagnosis, or treatment recommendations. It is an organisational tool only.
Always follow the guidance of your medical team. If you are worried about symptoms or side effects, use the contact numbers provided by your care team or seek urgent medical attention where appropriate.
Feedback and ideas are welcome – especially if they keep the app simple and genuinely useful.