From 4e426c19d08dceef7e25de6f98ad5239f96a783e Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Sat, 7 Nov 2020 09:47:56 -0800
Subject: [PATCH] Document chrono

---
 doc/api.rst    | 28 ++++++++++++++++++++--------
 doc/syntax.rst |  6 ++++++
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/doc/api.rst b/doc/api.rst
index 9b6c0f3c..67fad039 100644
--- a/doc/api.rst
+++ b/doc/api.rst
@@ -405,18 +405,30 @@ Using ``fmt::join``, you can separate tuple elements with a custom separator::
 Date and Time Formatting
 ========================
 
-The library supports `strftime
-<http://en.cppreference.com/w/cpp/chrono/c/strftime>`_-like date and time
-formatting::
+``fmt/chrono.h`` provides formatters for
+
+* `std::chrono::duration <https://en.cppreference.com/w/cpp/chrono/duration>`_
+* `std::chrono::time_point <https://en.cppreference.com/w/cpp/chrono/time_point>`_
+* `std::tm <https://en.cppreference.com/w/cpp/chrono/c/tm>`_
+
+For example::
 
   #include <fmt/chrono.h>
 
-  std::time_t t = std::time(nullptr);
-  // Prints "The date is 2016-04-29." (with the current date)
-  fmt::print("The date is {:%Y-%m-%d}.", fmt::localtime(t));
+  int main() {
+    using namespace std::literals::chrono_literals;
+    fmt::print("Default format: {} {}\n", 42s, 100ms);
+    fmt::print("strftime-like format: {:%H:%M:%S}\n", 3h + 15min + 30s);
+  }
 
-The format string syntax is described in the documentation of
-`strftime <http://en.cppreference.com/w/cpp/chrono/c/strftime>`_.
+prints::
+
+  Default format: 42s 100ms
+  strftime-like format: 03:15:30
+
+Chrono format specifications are described in :ref:`chrono-specs`.
+
+.. doxygenclass:: formatter<std::chrono::time_point<std::chrono::system_clock>, Char>
 
 .. _compile-api:
 
diff --git a/doc/syntax.rst b/doc/syntax.rst
index 4f859cf6..8557dd4b 100644
--- a/doc/syntax.rst
+++ b/doc/syntax.rst
@@ -321,6 +321,12 @@ Format specifications for chrono types have the following syntax:
               : "q" | "Q" | "r" | "R" | "S" | "t" | "T" | "u" | "U" | "V" |
               : "w" | "W" | "x" | "X" | "y" | "Y" | "z" | "Z" | "%" |
 
+Literal chars are copied unchanged to the output. Precision is valid only for
+``std::chrono::duration`` types with a floating-point representation type.
+
+*conversion_spec* are conversion specifiers documented in `strftime
+<http://en.cppreference.com/w/cpp/chrono/c/strftime>`_.
+
 .. _formatexamples:
 
 Format Examples