PostgreSQL has long been one of my favourite technologies. It's rock solid, has a huge array of features, and is extremely well documented.
I learned a lot about working with time and temporal data as I've been working with time series of geospatial data for many years. Dealing with time never gets easy - there's always one more thing that trips you up. There is also precious little information about more advanced topics.
This is why I wrote a book called "PostgreSQL: Time and Temporal Data". It provides a structured approach for working with time and time zones, and managing any kind of time-related data in the database.
I've also covered the same topics in a Pluralsight course.
Besides that, I made a tool to help with debugging complex SQL queries: pgdebug.
PostgreSQL time book | Pluralsight course | Postgres posts | pgdebug