This is actually three separate C++11/C++14 libraries:

1. "date.h" is a header-only library which builds upon <chrono>. It adds some new duration types, and new time_point types. It also adds "field" types such as year_month_day which is a struct {year, month, day}. And it provides convenient means to convert between the "field" types and the time_point types. See http://howardhinnant.github.io/date_v2.html for more details.

   Here is the Cppcon 2015 presentation on date.h: https://www.youtube.com/watch?v=tzyGjOm8AKo

   Here are the Cppcon 2015 slides on date.h: http://schd.ws/hosted_files/cppcon2015/43/hinnant_dates.pdf

2. "tz.h" / "tz.cpp" are a timezone library built on top of the "date.h" library. This timezone library is a complete parser of the IANA timezone database. It provides for an easy way to access all of the data in this database, using the types from "date.h" and <chrono>. The IANA database also includes data on leap seconds, and this library provides utilities to compute with that information as well. See http://howardhinnant.github.io/tz.html for more details. See the auto_download branch for an experimental version of this library which auto-installs the latest version of the IANA timezone database (if you are connected to the internet).

3. "iso_week.h" is a header-only library built on top of the "date.h" library which implements the ISO week date calendar. See http://howardhinnant.github.io/iso_week.html for more details.