Consider microseconds in maximum possible Calendar.ISO datetime (#7055)

Author: lexmag

lib/elixir/lib/calendar/iso.ex

@@ -17,7 +17,7 @@ defmodule Calendar.ISO do
 
   @unix_epoch 62167219200
   @unix_start 1_000_000 * -@unix_epoch
-  @unix_end 1_000_000 * (315569519999 - @unix_epoch)
+  @unix_end 315569519999999999 - @unix_epoch * 1_000_000
   @unix_range_microseconds @unix_start..@unix_end
 
   @type year :: 0..9999

lib/elixir/test/elixir/calendar_test.exs

@@ -230,12 +230,12 @@ defmodule DateTimeTest do
     assert DateTime.from_unix(-62167219201) == {:error, :invalid_unix_time}
 
     max_datetime = %DateTime{
-      calendar: Calendar.ISO, day: 31, hour: 23, microsecond: {0, 0},
+      calendar: Calendar.ISO, day: 31, hour: 23, microsecond: {999999, 6},
       minute: 59, month: 12, second: 59, std_offset: 0, time_zone: "Etc/UTC",
       utc_offset: 0, year: 9999, zone_abbr: "UTC"
     }
 
-    assert DateTime.from_unix(253402300799) == {:ok, max_datetime}
+    assert DateTime.from_unix(253402300799999999, :microsecond) == {:ok, max_datetime}
     assert DateTime.from_unix(253402300800) == {:error, :invalid_unix_time}
 
     minus_datetime = %DateTime{