Some highlights of the release are:
Starting from 18.0 Erlang/OTP is released under the APL 2.0 (Apache Public License)
erts: The time functionality has been extended. This includes a new API for
time, as well as "time warp" modes which alters the behavior when system time changes. You are strongly encouraged to use the new API instead of the old API based on erlang:now/0. erlang:now/0 has been deprecated since it is a scalability bottleneck.
For more information see the Time and Time Correction chapter of the ERTS User's Guide. Here is a link http://www.erlang.org/doc/apps/erts/time_correction.html
erts: Beside the API changes and time warp modes a lot of scalability and performance improvements regarding time management has been made. Examples are:
scheduler specific timer wheels,
scheduler specific BIF timer management,
parallel retrieval of monotonic time and system time on OS:es that support it.
erts: The previously introduced "eager check I/O" feature is now enabled by default.
erts/compiler: enhanced support for maps. Big maps new uses a HAMT (Hash Array Mapped Trie) representation internally which makes them more efficient. There is now also support for variables as map keys.
dialyzer: The -dialyzer() attribute can be used for suppressing warnings in a module by specifying functions or warning options. It can also be used for requesting warnings in a module. ssl: Remove default support for SSL-3.0 and added padding check for TLS-1.0 due to the Poodle vulnerability. ssl: Remove default support for RC4 cipher suites, as they are consider too weak. stdlib: Allow maps for supervisor flags and child specs stdlib: New functions in ets: take/2. Works the same as ets:delete/2 but also returns the deleted object(s). ets:update_counter/4 with a default object as argument