last_day_of_month -> days_in_month

Author: José Valim

lib/elixir/lib/calendar.ex

@@ -66,9 +66,9 @@ defmodule Calendar do
                        time_zone: time_zone, zone_abbr: zone_abbr, utc_offset: utc_offset, std_offset: std_offset}
 
   @doc """
-  Returns the last day of the month for the given year-month pair.
+  Returns how many days there are in the given year-month.
   """
-  @callback last_day_of_month(year, month) :: day
+  @callback days_in_month(year, month) :: day
 
   @doc """
   Returns true if the given year is a leap year.
@@ -175,6 +175,24 @@ defmodule Date do
     calendar.leap_year?(year)
   end
 
+  @doc """
+  Returns the number of days in the given date month.
+
+  ## Examples
+
+      iex> Date.days_in_month(~D[1900-01-13])
+      31
+      iex> Date.days_in_month(~D[1900-02-09])
+      28
+      iex> Date.days_in_month(~N[2000-02-20 01:23:45])
+      29
+
+  """
+  @spec days_in_month(Calendar.date) :: Calendar.day
+  def days_in_month(%{calendar: calendar, year: year, month: month}) do
+    calendar.days_in_month(year, month)
+  end
+
   @doc """
   Builds a new ISO date.
 

lib/elixir/lib/calendar/iso.ex

@@ -17,32 +17,32 @@ defmodule Calendar.ISO do
   @type day   :: 1..31
 
   @doc """
-  Returns the last day of the month for the given year.
+  Returns how many days there are in the given year-month.
 
   ## Examples
 
-      iex> Calendar.ISO.last_day_of_month(1900, 1)
+      iex> Calendar.ISO.days_in_month(1900, 1)
       31
-      iex> Calendar.ISO.last_day_of_month(1900, 2)
+      iex> Calendar.ISO.days_in_month(1900, 2)
       28
-      iex> Calendar.ISO.last_day_of_month(2000, 2)
+      iex> Calendar.ISO.days_in_month(2000, 2)
       29
-      iex> Calendar.ISO.last_day_of_month(2001, 2)
+      iex> Calendar.ISO.days_in_month(2001, 2)
       28
-      iex> Calendar.ISO.last_day_of_month(2004, 2)
+      iex> Calendar.ISO.days_in_month(2004, 2)
       29
-      iex> Calendar.ISO.last_day_of_month(2004, 4)
+      iex> Calendar.ISO.days_in_month(2004, 4)
       30
 
   """
-  @spec last_day_of_month(year, month) :: 28..31
-  def last_day_of_month(year, month)
+  @spec days_in_month(year, month) :: 28..31
+  def days_in_month(year, month)
 
-  def last_day_of_month(year, 2) do
+  def days_in_month(year, 2) do
     if leap_year?(year), do: 29, else: 28
   end
-  def last_day_of_month(_, month) when month in [4, 6, 9, 11], do: 30
-  def last_day_of_month(_, month) when month in 1..12, do: 31
+  def days_in_month(_, month) when month in [4, 6, 9, 11], do: 30
+  def days_in_month(_, month) when month in 1..12, do: 31
 
   @doc """
   Returns if the given year is a leap year.