diff --git a/CHANGELOG.md b/CHANGELOG.md
index cc79a0fe..f6e782b9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@
 - Add `Array.at` binding for returning an array item by its index. https://github.com/rescript-association/rescript-core/pull/48
 - Fixed type signatures of `Array.fromArrayLikeWithMap` and `Array.fromIteratorWithMap`. https://github.com/rescript-association/rescript-core/pull/50
 - Remove internal async/await helpers that do not need to be exposed in `Core`.
+- Add locale and formatting options to `localeDateString`, `localeString` and `localTimeString` functions https://github.com/rescript-association/rescript-core/pull/30
 
 ### Documentation
 
diff --git a/src/Core__Date.res b/src/Core__Date.res
index 5e8caf23..808fc48c 100644
--- a/src/Core__Date.res
+++ b/src/Core__Date.res
@@ -2,6 +2,20 @@ type t = Js.Date.t
 
 type time = float
 
+type localeOptions = {
+  dateStyle?: [#full | #long | #medium | #short],
+  timeStyle?: [#full | #long | #medium | #short],
+  weekday?: [#long | #short | #narrow],
+  era?: [#long | #short | #narrow],
+  year?: [#numeric | #"2-digit"],
+  month?: [#numeric | #"2-digit" | #long | #short | #narrow],
+  day?: [#numeric | #"2-digit"],
+  hour?: [#numeric | #"2-digit"],
+  minute?: [#numeric | #"2-digit"],
+  second?: [#numeric | #"2-digit"],
+  timeZoneName?: [#long | #short],
+}
+
 @send external valueOf: t => time = "valueOf"
 
 @new external make: unit => t = "Date"
@@ -146,8 +160,19 @@ external setUTCMinutesSMs: (t, ~minutes: int, ~seconds: int, ~milliseconds: int)
 @send external toTimeString: t => string = "toTimeString"
 
 @send external toLocaleDateString: t => string = "toLocaleDateString"
+@send external toLocaleDateStringWithLocale: (t, string) => string = "toLocaleDateString"
+@send
+external toLocaleDateStringWithLocaleAndOptions: (t, string, localeOptions) => string =
+  "toLocaleDateString"
 @send external toLocaleString: t => string = "toLocaleString"
+@send external toLocaleStringWithLocale: (t, string) => string = "toLocaleString"
+@send
+external toLocaleStringWithLocaleAndOptions: (t, string, localeOptions) => string = "toLocaleString"
 @send external toLocaleTimeString: t => string = "toLocaleTimeString"
+@send external toLocaleTimeStringWithLocale: (t, string) => string = "toLocaleTimeString"
+@send
+external toLocaleTimeStringWithLocaleAndOptions: (t, string, localeOptions) => string =
+  "toLocaleTimeString"
 
 @send external toISOString: t => string = "toISOString"
 @send external toUTCString: t => string = "toUTCString"
diff --git a/src/Core__Date.resi b/src/Core__Date.resi
new file mode 100644
index 00000000..5b3eab9a
--- /dev/null
+++ b/src/Core__Date.resi
@@ -0,0 +1,311 @@
+/***
+  Functions for interacting with JavaScript Dates.
+*/
+
+type t = Js.Date.t
+type time = float
+
+/**
+A type representing date time format options.
+
+Note: There are some properties missing:
+- fractionalSecondDigits
+- dayPeriod
+- calendar
+- numberingSystem
+- localeMatcher
+- timeZone
+- hour12
+- hourCycle
+- formatMatcher
+
+See full spec at https://tc39.es/ecma402/#datetimeformat-objects
+*/
+type localeOptions = {
+  dateStyle?: [#full | #long | #medium | #short],
+  timeStyle?: [#full | #long | #medium | #short],
+  weekday?: [#long | #narrow | #short],
+  era?: [#long | #narrow | #short],
+  year?: [#"2-digit" | #numeric],
+  month?: [#"2-digit" | #long | #narrow | #numeric | #short],
+  day?: [#"2-digit" | #numeric],
+  hour?: [#"2-digit" | #numeric],
+  minute?: [#"2-digit" | #numeric],
+  second?: [#"2-digit" | #numeric],
+  timeZoneName?: [#long | #short],
+}
+
+@send external valueOf: t => time = "valueOf"
+@new external make: unit => t = "Date"
+@new external fromString: string => t = "Date"
+@new external fromTime: time => t = "Date"
+@new external makeWithYM: (~year: int, ~month: int) => t = "Date"
+@new external makeWithYMD: (~year: int, ~month: int, ~date: int) => t = "Date"
+@new external makeWithYMDH: (~year: int, ~month: int, ~date: int, ~hours: int) => t = "Date"
+@new
+external makeWithYMDHM: (~year: int, ~month: int, ~date: int, ~hours: int, ~minutes: int) => t =
+  "Date"
+@new
+external makeWithYMDHMS: (
+  ~year: int,
+  ~month: int,
+  ~date: int,
+  ~hours: int,
+  ~minutes: int,
+  ~seconds: int,
+) => t = "Date"
+@new
+external makeWithYMDHMSM: (
+  ~year: int,
+  ~month: int,
+  ~date: int,
+  ~hours: int,
+  ~minutes: int,
+  ~seconds: int,
+  ~milliseconds: int,
+) => t = "Date"
+module UTC: {
+  @val external makeWithYM: (~year: int, ~month: int) => time = "Date.UTC"
+  @val external makeWithYMD: (~year: int, ~month: int, ~date: int) => time = "Date.UTC"
+  @val
+  external makeWithYMDH: (~year: int, ~month: int, ~date: int, ~hours: int) => time = "Date.UTC"
+  @val
+  external makeWithYMDHM: (
+    ~year: int,
+    ~month: int,
+    ~date: int,
+    ~hours: int,
+    ~minutes: int,
+  ) => time = "Date.UTC"
+  @val
+  external makeWithYMDHMS: (
+    ~year: int,
+    ~month: int,
+    ~date: int,
+    ~hours: int,
+    ~minutes: int,
+    ~seconds: int,
+  ) => time = "Date.UTC"
+  @val
+  external makeWithYMDHMSM: (
+    ~year: int,
+    ~month: int,
+    ~date: int,
+    ~hours: int,
+    ~minutes: int,
+    ~seconds: int,
+    ~milliseconds: int,
+  ) => time = "Date.UTC"
+}
+@val external now: unit => time = "Date.now"
+@send external getTime: t => time = "getTime"
+@send external getTimezoneOffset: t => int = "getTimezoneOffset"
+@send external getFullYear: t => int = "getFullYear"
+@send external getMonth: t => int = "getMonth"
+@send external getDate: t => int = "getDate"
+@send external getHours: t => int = "getHours"
+@send external getMinutes: t => int = "getMinutes"
+@send external getSeconds: t => int = "getSeconds"
+@send external getMilliseconds: t => int = "getMilliseconds"
+@send external getDay: t => int = "getDay"
+@send external setFullYear: (t, int) => unit = "setFullYear"
+@send external setFullYearM: (t, ~year: int, ~month: int) => unit = "setFullYear"
+@send external setFullYearMD: (t, ~year: int, ~month: int, ~date: int) => unit = "setFullYear"
+@send external setMonth: (t, int) => unit = "setMonth"
+@send external setDate: (t, int) => unit = "setDate"
+@send external setHours: (t, int) => unit = "setHours"
+@send external setHoursM: (t, ~hours: int, ~minutes: int) => unit = "setHours"
+@send external setHoursMS: (t, ~hours: int, ~minutes: int, ~seconds: int) => unit = "setHours"
+@send
+external setHoursMSMs: (t, ~hours: int, ~minutes: int, ~seconds: int, ~milliseconds: int) => unit =
+  "setHours"
+@send external setMinutes: (t, int) => unit = "setMinutes"
+@send external setMinutesS: (t, ~minutes: int, ~seconds: int) => unit = "setMinutes"
+@send
+external setMinutesSMs: (t, ~minutes: int, ~seconds: int, ~milliseconds: int) => unit = "setMinutes"
+@send external setSeconds: (t, int) => unit = "setSeconds"
+@send external setSecondsMs: (t, ~seconds: int, ~milliseconds: int) => unit = "setSeconds"
+@send external setMilliseconds: (t, int) => unit = "setMilliseconds"
+@send external setDay: (t, int) => unit = "setDay"
+@send external getUTCFullYear: t => int = "getUTCFullYear"
+@send external getUTCMonth: t => int = "getUTCMonth"
+@send external getUTCDate: t => int = "getUTCDate"
+@send external getUTCHours: t => int = "getUTCHours"
+@send external getUTCMinutes: t => int = "getUTCMinutes"
+@send external getUTCSeconds: t => int = "getUTCSeconds"
+@send external getUTCMilliseconds: t => int = "getUTCMilliseconds"
+@send external getUTCDay: t => int = "getUTCDay"
+@send external setUTCFullYear: (t, int) => unit = "setUTCFullYear"
+@send external setUTCFullYearM: (t, ~year: int, ~month: int) => unit = "setUTCFullYear"
+@send
+external setUTCFullYearMD: (t, ~year: int, ~month: int, ~date: int) => unit = "setUTCFullYear"
+@send external setUTCMonth: (t, int) => unit = "setUTCMonth"
+@send external setUTCDate: (t, int) => unit = "setUTCDate"
+@send external setUTCHours: (t, int) => unit = "setUTCHours"
+@send external setUTCHoursM: (t, ~hours: int, ~minutes: int) => unit = "setUTCHours"
+@send
+external setUTCHoursMS: (t, ~hours: int, ~minutes: int, ~seconds: int) => unit = "setUTCHours"
+@send
+external setUTCHoursMSMs: (
+  t,
+  ~hours: int,
+  ~minutes: int,
+  ~seconds: int,
+  ~milliseconds: int,
+) => unit = "setUTCHours"
+@send external setUTCMinutes: (t, int) => unit = "setUTCMinutes"
+@send external setUTCMinutesS: (t, ~minutes: int, ~seconds: int) => unit = "setUTCMinutes"
+@send
+external setUTCMinutesSMs: (t, ~minutes: int, ~seconds: int, ~milliseconds: int) => unit =
+  "setUTCMinutes"
+@send external setUTCSeconds: (t, int) => unit = "setUTCSeconds"
+@send external setUTCSecondsMs: (t, ~seconds: int, ~milliseconds: int) => unit = "setUTCSeconds"
+@send external setUTCMilliseconds: (t, int) => unit = "setUTCMilliseconds"
+@send external setUTCDay: (t, int) => unit = "setUTCDay"
+@send external toDateString: t => string = "toDateString"
+@send external toString: t => string = "toString"
+@send external toTimeString: t => string = "toTimeString"
+
+/** 
+`toLocaleDateString(date)`
+
+Converts a JavaScript date to a localized date string. It will use the current locale.
+
+## Examples
+```rescript
+Date.make()->Date.toLocaleDateString->Console.log
+// 2/19/2023
+```
+*/
+@send
+external toLocaleDateString: t => string = "toLocaleDateString"
+
+/** 
+`toLocaleDateStringWithLocale(date, locale)`
+
+Converts a JavaScript date to a localized date string. It will use the specified locale.
+
+## Examples
+```rescript
+Date.make()->Date.toLocaleDateStringWithLocale("en-US")->Console.log
+// 2/19/2023
+```
+*/
+@send
+external toLocaleDateStringWithLocale: (t, string) => string = "toLocaleDateString"
+
+/** 
+`toLocaleDateStringWithLocaleAndOptions(date, locale, options)`
+
+Converts a JavaScript date to a localized date string. It will use the specified locale and formatting options.
+
+## Examples
+```rescript
+Date.make()->Date.toLocaleDateStringWithLocaleAndOptions("en-US", { dateStyle: #long })->Console.log
+// February 19, 2023
+
+Date.make()->Date.toLocaleDateStringWithLocaleAndOptions("de", { hour: #"2-digit", minute: #"2-digit" })->Console.log
+// 19.2.2023, 15:40
+
+Date.make()->Date.toLocaleDateStringWithLocaleAndOptions("de", { year: #numeric })->Console.log
+// 2023
+```
+*/
+@send
+external toLocaleDateStringWithLocaleAndOptions: (t, string, localeOptions) => string =
+  "toLocaleDateString"
+
+/** 
+`toLocaleString(date)`
+
+Converts a JavaScript date to a localized date-time string. It will use the current locale.
+
+## Examples
+```rescript
+Date.make()->Date.toLocaleString->Console.log
+// 2/19/2023, 3:40:00 PM
+```
+*/
+@send
+external toLocaleString: t => string = "toLocaleString"
+
+/** 
+`toLocaleStringWithLocale(date, locale)`
+
+Converts a JavaScript date to a localized date-time string. It will use the specified locale.
+
+## Examples
+```rescript
+Date.make()->Date.toLocaleStringWithLocale("en-US")->Console.log
+// 2/19/2023, 3:40:00 PM
+```
+*/
+@send
+external toLocaleStringWithLocale: (t, string) => string = "toLocaleString"
+
+/** 
+`toLocaleStringWithLocaleAndOptions(date, locale, options)`
+
+Converts a JavaScript date to a localized date-time string. It will use the specified locale and formatting options.
+
+## Examples
+```rescript
+Date.make()->Date.toLocaleStringWithLocaleAndOptions("en", { dateStyle: #short, timeStyle: #short })->Console.log
+// 2/19/23, 3:40 PM
+
+Date.make()->Date.toLocaleStringWithLocaleAndOptions("en", { era: #long, year: #numeric, month: #"2-digit", day: #"2-digit", hour: #numeric, timeZoneName: #short })->Console.log
+// 02/19/2023 Anno Domini, 3 PM GMT+1
+```
+*/
+@send
+external toLocaleStringWithLocaleAndOptions: (t, string, localeOptions) => string = "toLocaleString"
+
+/** 
+`toLocaleTimeString(date)`
+
+Converts a JavaScript date to a localized time string. It will use the current locale.
+
+## Examples
+```rescript
+Date.make()->Date.toLocaleTimeString->Console.log
+// 3:40:00 PM
+```
+*/
+@send
+external toLocaleTimeString: t => string = "toLocaleTimeString"
+
+/** 
+`toLocaleTimeStringWithLocale(date, locale)`
+
+Converts a JavaScript date to a localized time string. It will use the specified locale.
+
+## Examples
+```rescript
+Date.make()->Date.toLocaleTimeStringWithLocale("en-US")->Console.log
+// 3:40:00 PM
+```
+*/
+@send
+external toLocaleTimeStringWithLocale: (t, string) => string = "toLocaleTimeString"
+
+/** 
+`toLocaleTimeStringWithLocaleAndOptions(date, locale, options)`
+
+Converts a JavaScript date to a localized time string. It will use the specified locale and formatting options.
+
+## Examples
+```rescript
+Date.make()->Date.toLocaleTimeStringWithLocaleAndOptions("en-US", { timeStyle: #long })->Console.log
+// 3:40:00 PM GMT+1
+
+Date.make()->Date.toLocaleTimeStringWithLocaleAndOptions("de", { hour: #"2-digit", minute: #"2-digit" })->Console.log
+// 15:40
+```
+*/
+@send
+external toLocaleTimeStringWithLocaleAndOptions: (t, string, localeOptions) => string =
+  "toLocaleTimeString"
+
+@send external toISOString: t => string = "toISOString"
+@send external toUTCString: t => string = "toUTCString"
+@return(nullable) @send external toJSON: t => option<string> = "toJSON"