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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
This. And if you really need a period tracker: use free & open-source period tracker apps (like this one for Android) that do not use internet permissions. This way you can make sure there are no trackers, and your data isn't being sent somewhere else (staying on device).
NOTE:
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