Introduction

This tutorial explains how to modify an ICS (iCalendar) to control how calendar dates are displayed on the device, including Workdays, Special Workdays, Holidays, and Non-Workdays.

What Is an ICS File?

An ICS file is a standard calendar file format used to store event data. By editing specific fields, you can define how dates are categorized and displayed on supported devices.

Prerequisites

• Text editor: Any plain-text editor (Notepad, TextEdit). Editors like Notepad++ or VS Code are recommended.
• ICS file: Export from Google Calendar, Outlook, or download from a calendar provider.

Step 1: Obtain the ICS File

Export or download the ICS file and open it using a text editor.

Step 2: Display Style Configuration

The device supports a global custom field called X-GRANDSTREAM-STYLE, which controls how calendar categories are interpreted:

Available Styles

• Special Workdays & Holidays

X-GRANDSTREAM-STYLE:COMMON

Workdays & Non-Workdays

X-GRANDSTREAM-STYLE:WORK

Style Behavior

• COMMON
  • CATEGORIES:WORKDAY → Special Workday
  • CATEGORIES:HOLIDAY → Holiday
• WORK
  • Weekends (Saturday & Sunday) are non-working days by default.
  • If WORKDAY or HOLIDAY markers exist in a month, they override the default behavior.
  • If no markers exist, weekends are automatically treated as holidays.

Step 3: Define Event Categories

Inside each VEVENT, add or edit the CATEGORIES field (place it before END:VEVENT):

Supported Values

• Holiday

CATEGORIES:HOLIDAY

• Workday

CATEGORIES:WORKDAY

• Non-Workday

Any other value, or leave CATEGORIES unset.

Example

BEGIN:VEVENT
DTSTART:20251225T000000
DTEND:20251225T235959
SUMMARY:Christmas
CATEGORIES:HOLIDAY
END:VEVENT

Conflict Resolution Rules

• When multiple ICS files define the same date, file priority determines which marker applies.
• When multiple ICS files define X-GRANDSTREAM-STYLE, the style from the higher-priority file is used.
• Within a single ICS file, if both WORKDAY and HOLIDAY are assigned to the same date, WORKDAY takes precedence.

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