feat(datetime): update weekdays abbreviation for ionic theme

Author: OS-giulianasilva

core/src/components/datetime/utils/data.ts

@@ -65,8 +65,8 @@ const hour24 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 1
 /**
  * Given a locale and a theme,
  * return an array with formatted days
- * of the week. iOS should display days
- * such as "Mon" or "Tue".
+ * of the week. iOS and Ionic themes should 
+ * display days such as "Mon" or "Tue".
  * MD should display days such as "M"
  * or "T".
  */
@@ -76,7 +76,7 @@ export const getDaysOfWeek = (locale: string, theme: Theme, firstDayOfWeek = 0)
    * ion-datetime assumes weeks start on Sunday,
    * but is configurable via `firstDayOfWeek`.
    */
-  const weekdayFormat = theme === 'ios' ? 'short' : 'narrow';
+  const weekdayFormat = theme === 'md' ? 'narrow' : 'short';
   const intl = new Intl.DateTimeFormat(locale, { weekday: weekdayFormat });
   const startDate = new Date('11/01/2020');
   const daysOfWeek = [];