Introduce julian.h

README.md

@@ -1,6 +1,6 @@
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-This is actually three separate C++11/C++14 libraries:
+This is actually several 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/date.html for more details.
 
@@ -12,6 +12,8 @@ This is actually three separate C++11/C++14 libraries:
 
 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/date/iso_week.html for more details.
 
+4. `"julean.h"` is a header-only library built on top of the `"date.h"` library which implements a proleptic Julian calendar which is fully interoperable with everything above.  See http://howardhinnant.github.io/date/julian.html for more details.
+
 There has been a recent change in the library design.  If you are trying to migrate from the previous design, rename `day_point` to `sys_days` everywhere, and that ought to bring the number of errors down to a small roar.
 
 `"date.h"` and `"tz.h"` are now proposed for standardization here:  http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0355r0.html