Fix documentation for format* props

Fixes #165

README.md

@@ -87,9 +87,9 @@ Displays a complete, interactive calendar.
 |activeStartDate|The beginning of a period that shall be displayed by default when no value is given. Defaults to today.|`new Date(2017, 0, 1)`|
 |calendarType|Defines which type of calendar should be used. Can be "ISO 8601", "US", "Arabic", or "Hebrew". Defaults to a calendar most commonly used in specific locale. Setting to "US" or "Hebrew" will change the first day of the week to Sunday. Setting to "Arabic" will change the first day of the week to Saturday. Setting to "Arabic" or "Hebrew" will make weekends appear on Friday to Saturday.|`"ISO 8601"`|
 |className|Defines class name(s) that will be added along with "react-calendar" to the main React-Calendar `<div>` element.|<ul><li>String: `"class1 class2"`</li><li>Array of strings: `["class1", "class2 class3"]`</li></ul>|
-|formatMonth|Function called to override default formatting of month names. Can be used to use your own formatting function.|`(value) => formatDate(value, 'MMM')`|
-|formatMonthYear|Function called to override default formatting of month and year in the top navigation section. Can be used to use your own formatting function.|`(value) => formatDate(value, 'MMMM YYYY')`|
-|formatShortWeekday|Function called to override default formatting of weekday names. Can be used to use your own formatting function.|`(value) => formatDate(value, 'dd')`|
+|formatMonth|Function called to override default formatting of month names. Can be used to use your own formatting function.|`(locale, date) => formatDate(date, 'MMM')`|
+|formatMonthYear|Function called to override default formatting of month and year in the top navigation section. Can be used to use your own formatting function.|`(locale, date) => formatDate(date, 'MMMM YYYY')`|
+|formatShortWeekday|Function called to override default formatting of weekday names. Can be used to use your own formatting function.|`(locale, date) => formatDate(date, 'dd')`|
 |locale|Defines which locale should be used by the calendar. Can be any [IETF language tag](https://en.wikipedia.org/wiki/IETF_language_tag). Defaults to user's browser settings.|`"hu-HU"`|
 |maxDate|Defines maximum date that the user can select. Periods partially overlapped by maxDate will also be selectable, although react-calendar will ensure that no later date is selected.|Date: `new Date()`|
 |maxDetail|Defines the most detailed view that the user shall see. View defined here also becomes the one on which clicking an item will select a date and pass it to onChange. Can be "month", "year", "decade" or "century". Defaults to "month".|`"month"`|

index.d.ts

@@ -3,7 +3,7 @@ declare module "react-calendar" {
   type Detail = "month" | "year" | "decade" | "century"
   type DateCallback = (date: Date) => void
   type OnChangeDateCallback = (date: Date | Date[]) => void
-  type FormatterCallback = (date: Date) => string
+  type FormatterCallback = (locale: string, date: Date) => string
   type ViewCallback = (props: ViewCallbackProperties) => void
 
   export default function Calendar(props: CalendarProps): JSX.Element;