I was hell bent on reinventing the wheel. Gung ho even. But then, while searching for plaintext productivity file ideas, I stumbled across Remind[0]. Holy shit. This is the way. I completely stopped what I was doing and installed it. The file format is easy. What you do with it can also be easy, or not. Up to you. I put my reccurring entries in, payday, birthdays, etc. Followed by what I had going on at work. Setup a cron job under my user account on the Raspberry Pi of Judgement to email me a calendar daily. But I could do better, so I started writing code to generate ics files... When I realized this was probably already done. A search later, and yeah, several times over.
So all told, the script I run in cron is here[1]. A ical file is generated and attached to an email daily at 0330 (seven minutes before I wake up). Open in K9 mail on my phone, single touch import the ical file into my calendar app. Boom. I am digging this. Everything is in text files as I desired.
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https://www.roaringpenguin.com/products/remind
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