diff --git a/src/runtime/includes/formatters.ts b/src/runtime/includes/formatters.ts
index 3c9ccfb..69f9214 100644
--- a/src/runtime/includes/formatters.ts
+++ b/src/runtime/includes/formatters.ts
@@ -6,6 +6,16 @@ import { getOptions } from '../configs'
 
 import { monadicMemoize } from './memoize'
 
+type MemoizedNumberFormatterFactory = MemoizedIntlFormatter<
+  Intl.NumberFormat,
+  Intl.NumberFormatOptions
+>
+
+type MemoizedDateTimeFormatterFactory = MemoizedIntlFormatter<
+  Intl.DateTimeFormat,
+  Intl.DateTimeFormatOptions
+>
+
 const getIntlFormatterOptions = (
   type: 'time' | 'number' | 'date',
   name: string
@@ -18,57 +28,66 @@ const getIntlFormatterOptions = (
   throw new Error(`[svelte-i18n] Unknown "${name}" ${type} format.`)
 }
 
-const createNumberFormatter: MemoizedIntlFormatter<
-  Intl.NumberFormat,
-  Intl.NumberFormatOptions
-> = monadicMemoize(({ locale, format, ...options }) => {
-  if (locale == null) {
-    throw new Error('[svelte-i18n] A "locale" must be set to format numbers')
+const createNumberFormatter: MemoizedNumberFormatterFactory = monadicMemoize(
+  ({ locale, format, ...options }) => {
+    if (locale == null) {
+      throw new Error('[svelte-i18n] A "locale" must be set to format numbers')
+    }
+
+    if (format) {
+      options = getIntlFormatterOptions('number', format)
+    }
+
+    return new Intl.NumberFormat(locale, options)
   }
+)
 
-  if (format) {
-    options = getIntlFormatterOptions('number', format)
+const createDateFormatter: MemoizedDateTimeFormatterFactory = monadicMemoize(
+  ({ locale, format, ...options }) => {
+    if (locale == null) {
+      throw new Error('[svelte-i18n] A "locale" must be set to format dates')
+    }
+
+    if (format) options = getIntlFormatterOptions('date', format)
+    else if (Object.keys(options).length === 0) {
+      options = getIntlFormatterOptions('date', 'short')
+    }
+
+    return new Intl.DateTimeFormat(locale, options)
   }
+)
 
-  return new Intl.NumberFormat(locale, options)
-})
-export const getNumberFormatter = ({ locale = getCurrentLocale(), ...args } = {}) => createNumberFormatter({ locale, ...args })
+const createTimeFormatter: MemoizedDateTimeFormatterFactory = monadicMemoize(
+  ({ locale, format, ...options }) => {
+    if (locale == null) {
+      throw new Error(
+        '[svelte-i18n] A "locale" must be set to format time values'
+      )
+    }
 
-const createDateFormatter: MemoizedIntlFormatter<
-  Intl.DateTimeFormat,
-  Intl.DateTimeFormatOptions
-> = monadicMemoize(({ locale, format, ...options }) => {
-  if (locale == null) {
-    throw new Error('[svelte-i18n] A "locale" must be set to format dates')
+    if (format) options = getIntlFormatterOptions('time', format)
+    else if (Object.keys(options).length === 0) {
+      options = getIntlFormatterOptions('time', 'short')
+    }
+
+    return new Intl.DateTimeFormat(locale, options)
   }
+)
 
-  if (format) options = getIntlFormatterOptions('date', format)
-  else if (Object.keys(options).length === 0) {
-    options = getIntlFormatterOptions('date', 'short')
-  }
+export const getNumberFormatter: MemoizedNumberFormatterFactory = ({
+  locale = getCurrentLocale(),
+  ...args
+} = {}) => createNumberFormatter({ locale, ...args })
 
-  return new Intl.DateTimeFormat(locale, options)
-})
-export const getDateFormatter = ({ locale = getCurrentLocale(), ...args } = {}) => createDateFormatter({ locale, ...args })
+export const getDateFormatter: MemoizedDateTimeFormatterFactory = ({
+  locale = getCurrentLocale(),
+  ...args
+} = {}) => createDateFormatter({ locale, ...args })
 
-const createTimeFormatter: MemoizedIntlFormatter<
-  Intl.DateTimeFormat,
-  Intl.DateTimeFormatOptions
-> = monadicMemoize(({ locale, format, ...options }) => {
-  if (locale == null) {
-    throw new Error(
-      '[svelte-i18n] A "locale" must be set to format time values'
-    )
-  }
-
-  if (format) options = getIntlFormatterOptions('time', format)
-  else if (Object.keys(options).length === 0) {
-    options = getIntlFormatterOptions('time', 'short')
-  }
-
-  return new Intl.DateTimeFormat(locale, options)
-})
-export const getTimeFormatter = ({ locale = getCurrentLocale(), ...args } = {}) => createTimeFormatter({ locale, ...args })
+export const getTimeFormatter: MemoizedDateTimeFormatterFactory = ({
+  locale = getCurrentLocale(),
+  ...args
+} = {}) => createTimeFormatter({ locale, ...args })
 
 export const getMessageFormatter = monadicMemoize(
   (message: string, locale: string = getCurrentLocale()) =>