fix(datetime): revert phosphor icons removal

Author: brandyscarney

core/src/components/datetime/datetime.tsx

@@ -1,3 +1,5 @@
+import caretLeftRegular from '@phosphor-icons/core/assets/regular/caret-left.svg';
+import caretRightRegular from '@phosphor-icons/core/assets/regular/caret-right.svg';
 import type { ComponentInterface, EventEmitter } from '@stencil/core';
 import { Component, Element, Event, Host, Method, Prop, State, Watch, h, writeTask } from '@stencil/core';
 import { startFocusVisible } from '@utils/focus-visible';
@@ -2627,19 +2629,45 @@ export class Datetime implements ComponentInterface {
   }
 
   /**
-   * Get the next month icon from the config.
+   * Get the icon to use for the next icon.
+   * Otherwise, use the icon set in the config.
    * If no icon is set in the config, use the default icon.
    */
   get datetimeNextIcon(): string {
-    return config.get('datetimeNextIcon', chevronForward);
+    // Determine the theme and map to default icons
+    const theme = getIonTheme(this);
+    const defaultIcons = {
+      ios: chevronForward,
+      ionic: caretRightRegular,
+      md: chevronForward,
+    };
+
+    // Get the default icon based on the theme, falling back to 'md' icon if necessary
+    const defaultIcon = defaultIcons[theme] || defaultIcons.md;
+
+    // Return the configured datetime next icon or the default icon
+    return config.get('datetimeNextIcon', defaultIcon);
   }
 
   /**
-   * Get the previous month icon from the config.
+   * Get the icon to use for the previous icon.
+   * Otherwise, use the icon set in the config.
    * If no icon is set in the config, use the default icon.
    */
   get datetimePreviousIcon(): string {
-    return config.get('datetimePreviousIcon', chevronBack);
+    // Determine the theme and map to default icons
+    const theme = getIonTheme(this);
+    const defaultIcons = {
+      ios: chevronBack,
+      ionic: caretLeftRegular,
+      md: chevronBack,
+    };
+
+    // Get the default icon based on the theme, falling back to 'md' icon if necessary
+    const defaultIcon = defaultIcons[theme] || defaultIcons.md;
+
+    // Return the configured datetime previous icon or the default icon
+    return config.get('datetimePreviousIcon', defaultIcon);
   }
 
   /**