I often make these same timelines in excel manually and paste them into a powerpoint.
I am curious to know the tech stack you used -- or if you have a github for scourcecode.
I am working on a writeup with some development details.
Here is the stack:
• Alpinejs as a framework
• Chrono for date parsing (try typing "next Tuesday" into the date input)
• Dayjs for date formatting and operations.
• flatpickr for the date picker
• xslx-populate for export. There are a LOT of JS->excel utilities out there.
• Tailwind for styling.
• No back-end, no database. All static files.
Don't let that stop you from looking at it with view-source. It's literally two files :)