Date and time library based on the C++11/14/17 <chrono> header
Description
This is actually several separate C++11/C++14/C++17 libraries:
- "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.
- "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.
Slightly modified versions of "date.h" and "tz.h" were voted into
the C++20 standard.
