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+# Custom Locale Data
+
+This folder is used to store custom locale data. These custom locale data are
+not yet provided by [Unicode Common Locale Data Repository](http://cldr.unicode.org/development/new-cldr-developers)
+and hence not provided in [react-intl/locale-data/*](https://github.com/yahoo/react-intl).
+
+The locale data should support [Locale Data APIs](https://github.com/yahoo/react-intl/wiki/API#locale-data-apis)
+of the react-intl library.
+
+It is recommended to start your custom locale data from this sample English
+locale data ([*](#plural-rules)):
+
+```javascript
+/*eslint eqeqeq: "off"*/
+/*eslint no-nested-ternary: "off"*/
+
+export default [
+  {
+    locale: "en",
+    pluralRuleFunction: function(e, a) {
+      var n = String(e).split("."),
+        l = !n[1],
+        o = Number(n[0]) == e,
+        t = o && n[0].slice(-1),
+        r = o && n[0].slice(-2);
+      return a ? 1 == t && 11 != r ? "one" : 2 == t && 12 != r ? "two" : 3 == t && 13 != r ? "few" : "other" : 1 == e && l ? "one" : "other"
+    },
+    fields: {
+      year: {
+        displayName: "year",
+        relative: {
+          0: "this year",
+          1: "next year",
+          "-1": "last year"
+        },
+        relativeTime: {
+          future: {
+            one: "in {0} year",
+            other: "in {0} years"
+          },
+          past: {
+            one: "{0} year ago",
+            other: "{0} years ago"
+          }
+        }
+      },
+      month: {
+        displayName: "month",
+        relative: {
+          0: "this month",
+          1: "next month",
+          "-1": "last month"
+        },
+        relativeTime: {
+          future: {
+            one: "in {0} month",
+            other: "in {0} months"
+          },
+          past: {
+            one: "{0} month ago",
+            other: "{0} months ago"
+          }
+        }
+      },
+      day: {
+        displayName: "day",
+        relative: {
+          0: "today",
+          1: "tomorrow",
+          "-1": "yesterday"
+        },
+        relativeTime: {
+          future: {
+            one: "in {0} day",
+            other: "in {0} days"
+          },
+          past: {
+            one: "{0} day ago",
+            other: "{0} days ago"
+          }
+        }
+      },
+      hour: {
+        displayName: "hour",
+        relativeTime: {
+          future: {
+            one: "in {0} hour",
+            other: "in {0} hours"
+          },
+          past: {
+            one: "{0} hour ago",
+            other: "{0} hours ago"
+          }
+        }
+      },
+      minute: {
+        displayName: "minute",
+        relativeTime: {
+          future: {
+            one: "in {0} minute",
+            other: "in {0} minutes"
+          },
+          past: {
+            one: "{0} minute ago",
+            other: "{0} minutes ago"
+          }
+        }
+      },
+      second: {
+        displayName: "second",
+        relative: {
+          0: "now"
+        },
+        relativeTime: {
+          future: {
+            one: "in {0} second",
+            other: "in {0} seconds"
+          },
+          past: {
+            one: "{0} second ago",
+            other: "{0} seconds ago"
+          }
+        }
+      }
+    }
+  }
+]
+
+```
+
+## Notes
+
+### Plural Rules
+
+The function `pluralRuleFunction()` should return the key to proper string of
+a plural form(s). The purpose of the function is to provide key of translate
+strings of correct plural form according. The different forms are described in
+[CLDR's Plural Rules][cldr-plural-rules],
+
+[cldr-plural-rules]: http://cldr.unicode.org/index/cldr-spec/plural-rules
+
+#### Quick Overview on CLDR Rules
+
+Let's take English as an example.
+
+When you describe a number, you can be either describe it as:
+* Cardinals: 1st, 2nd, 3rd ... 11th, 12th ... 21st, 22nd, 23nd ....
+* Ordinals: 1, 2, 3 ...
+
+In any of these cases, the nouns will reflect the number with singular or plural
+form. For example:
+* in 0 days
+* in 1 day
+* in 2 days
+
+The `pluralRuleFunction` receives 2 parameters:
+* `e`: a string representation of the number. Such as, "`1`", "`2`", "`2.1`".
+* `a`: `true` if this is "cardinal" type of description. `false` for ordinal and other case.
+
+#### How you should write `pluralRuleFunction`
+
+The first rule to write pluralRuleFunction is never translate the output string
+into your language. [Plural Rules][cldr-plural-rules] specified you should use
+these as the return values:
+
+  * "`zero`"
+  * "`one`" (singular)
+  * "`two`" (dual)
+  * "`few`" (paucal)
+  * "`many`" (also used for fractions if they have a separate class)
+  * "`other`" (required—general plural form—also used if the language only has a single form)
+
+Again, we'll use English as the example here.
+
+Let's read the `return` statement in the pluralRuleFunction above:
+```javascript
+  return a ? 1 == t && 11 != r ? "one" : 2 == t && 12 != r ? "two" : 3 == t && 13 != r ? "few" : "other" : 1 == e && l ? "one" : "other"
+```
+
+This nested ternary is hard to read. It basically means:
+```javascript
+// e: the number variable to examine
+// a: "true" if cardinals
+// l: "true" if the variable e has nothin after decimal mark (e.g. "1.0" would be false)
+// o: "true" if the variable e is an integer
+// t: the "ones" of the number. e.g. "3" for number "9123"
+// r: the "ones" and "tens" of the number. e.g. "23" for number "9123"
+if (a == true) {
+  if (t == 1 && r != 11) {
+    return "one"; // i.e. 1st, 21st, 101st, 121st ...
+  } else if (t == 2 && r != 12) {
+    return "two"; // i.e. 2nd, 22nd, 102nd, 122nd ...
+  } else if (t == 3 && r != 13) {
+    return "few"; // i.e. 3rd, 23rd, 103rd, 123rd ...
+  } else {
+    return "other"; // i.e. 4th, 11th, 12th, 24th ...
+  }
+} else {
+  if (e == 1 && l) {
+    return "one"; // i.e. 1 day
+  } else {
+    return "other"; // i.e. 0 days, 2 days, 3 days
+  }
+}
+```
+
+If your language, like French, do not have complicated cardinal rules, you may
+use the French's version of it:
+```javascript
+function (e, a) {
+  return a ? 1 == e ? "one" : "other" : e >= 0 && e < 2 ? "one" : "other";
+}
+```
+
+If your language, like Chinese, do not have any pluralization rule at all you
+may use the Chinese's version of it:
+```javascript
+function (e, a) {
+  return "other";
+}
+```