Using only the bare language, every task is tedious (in any language). Using a suitable library any task can be reasonably simple.
The standard library has steadily grown over the years. Its description in the standard is now larger than that of the language features.
SL.1: Use libraries wherever possible
Save time. Don't re-invent the wheel. Don't replicate the work of others. Benefit from other people's work when they make improvements. Help other people when you make improvements.
SL.2: Prefer the standard library to other libraries
More people know the standard library. It is more likely to be stable, well-maintained, and widely available than your own code or most other libraries.
SL.3: Do not add non-standard entities to namespace std
Adding to std might change the meaning of otherwise standards conforming code. Additions to std might clash with future versions of the standard.
SL.4: Use the standard library in a type-safe manner
Because, obviously, breaking this rule can lead to undefined behavior, memory corruption, and all kinds of other bad errors.
Note: This is a semi-philosophical meta-rule, which needs many supporting concrete rules. We need it as an umbrella for the more specific rules.
SL.regex: Regex
<regex> is the standard C++ regular expression library. It supports a variety of regular expression pattern conventions.
SL.chrono: Time
<chrono> (defined in namespace std::chrono) provides the notions of time_point and duration together with functions for outputting time in various units.