New Outlook Custom Holiday Files Gap for Classic Outlook Users: Temporary Options

Classic Outlook for Windows lets you import custom holiday files (.hol) to add non-standard holidays to your calendar. The new Outlook for Windows does not support .hol files at all. This leaves users who rely on regional or company-specific holidays without a direct migration path. This article explains the technical gap, provides temporary workarounds using manual calendar entries and CSV imports, and lists limitations you must expect until Microsoft adds native support.

Why Classic Outlook’s Holiday File Feature Does Not Work in New Outlook

Classic Outlook stores holiday definitions in .hol files, a legacy binary format introduced in early Outlook versions. The new Outlook for Windows is built on a different codebase that uses Microsoft Graph and Exchange Web Services for calendar data. The .hol file format is not part of that architecture. Microsoft has not announced any timeline for adding .hol support to the new Outlook. As a result, users who upgrade to new Outlook lose the ability to import custom holiday sets — even if those sets were created or used in classic Outlook.

The holiday file feature in classic Outlook reads a plain-text .hol file that contains holiday names and recurrence rules. New Outlook’s calendar engine does not parse this format. The only holidays that appear automatically in new Outlook are those supplied by Microsoft’s built-in holiday calendar for your region, which you can toggle on in Settings > Calendar > Holidays. Custom holidays from a .hol file are ignored entirely.

Temporary Workarounds to Add Custom Holidays in New Outlook

Until Microsoft adds native .hol support, you have three workarounds. Each has trade-offs in effort and accuracy.

Workaround 1: Manual Entry of Each Holiday

For a small number of holidays, manual entry is the fastest method. This works best when you have ten or fewer holiday dates to add.

1. Open the new Outlook calendar
   Click the Calendar icon in the left navigation pane.
2. Create a new calendar for holidays
   Right-click My Calendars and select Add calendar > Create blank calendar. Name it “Company Holidays” or “Regional Holidays.”
3. Add a holiday event
   Double-click the date of the holiday. In the event window, enter the holiday name as the title. Set the time to All day. Click Save.
4. Repeat for each holiday
   Repeat step 3 for every date in your .hol file. Recurring holidays such as “First Monday of September” must be added as a recurring event by selecting the Repeat option in the event window.

Workaround 2: CSV Import via Outlook on the Web

New Outlook does not have a direct CSV import for calendar events. However, Outlook on the web (the browser version) allows you to import CSV files into a calendar. You can then sync that calendar to the new Outlook app.

1. Create a CSV file with your holidays
   Use Excel or a text editor to create a CSV file with these columns: Subject, Start Date, Start Time, End Date, End Time, All Day Event. Each holiday gets one row. For an all-day event, set Start Time and End Time to blank and All Day Event to TRUE.
2. Sign in to Outlook on the web
   Go to outlook.office.com and sign in with your Microsoft 365 or Outlook.com account.
3. Open the Calendar
   Click the Calendar icon in the web app.
4. Import the CSV
   Click Add calendar > Import from CSV. Select your CSV file. The holidays appear as a new calendar called “Imported.”
5. View the imported calendar in new Outlook
   In the new Outlook desktop app, the imported calendar appears under My Calendars. You can rename it if needed.

Workaround 3: Use a Third-Party Tool to Convert .hol to ICS

ICS (iCalendar) files are supported by new Outlook. Several free online tools convert .hol files to ICS format. After conversion, you can import the ICS file directly into new Outlook.

1. Locate your .hol file
   In classic Outlook, go to File > Options > Calendar > Add Holidays. The .hol files are stored in C:\Program Files\Microsoft Office\root\Office16\Holidays or a similar path depending on your Office version.
2. Convert the .hol file to ICS
   Use a trusted online converter such as Convertio or a local script. Upload the .hol file and download the resulting ICS file.
3. Import the ICS file into new Outlook
   In new Outlook, click File > Open & Export > Import/Export > Import an iCalendar (.ics) file. Select the ICS file and choose to import it as a new calendar or merge it into an existing one.

Limitations and Things to Avoid with These Workarounds

Manual entry does not scale

If your .hol file contains more than 20 holidays, manual entry becomes error-prone. Recurrence rules for floating holidays such as “Easter” or “Thanksgiving” are difficult to set correctly without a reference. Use the CSV or ICS method instead.

CSV import via Outlook on the web may not sync instantly

After importing a CSV, the new calendar may take several minutes to appear in the new Outlook desktop app. Force a sync by clicking the Send/Receive button on the ribbon or restarting the app.

Third-party converters may alter recurrence rules

Some free online converters do not handle complex recurrence rules correctly. Test the ICS file by importing it into a test calendar first. Verify that recurring holidays such as “Second Monday of October” appear on the correct dates.

Do not modify the registry to force .hol support

Some online guides suggest editing the Windows Registry to enable .hol import in new Outlook. This action is unsupported and can break the app. Microsoft has confirmed that .hol is not part of new Outlook’s architecture. Registry edits will not add the feature and may cause crashes.

Classic Outlook Holiday File vs New Outlook Calendar Import: Key Differences

Item	Classic Outlook (.hol)	New Outlook (ICS / CSV)
File format	.hol (legacy binary)	.ics (iCalendar) or .csv
Recurrence support	Native support for complex rules like “Easter”	Full support for RRULE in ICS; CSV requires manual recurrence
Import location	Directly into default Calendar	New calendar or merged into existing
Sync behavior	Imported holidays stay in the mailbox	ICS imports are static; CSV imports sync via Exchange
Microsoft support	Deprecated in new Outlook	Actively supported

You can now add custom holidays to new Outlook using manual entry, CSV import through Outlook on the web, or ICS conversion from your existing .hol files. These workarounds are temporary until Microsoft adds native holiday file support. For recurring holidays with complex rules, the ICS conversion method is the most accurate. To stay informed, monitor the Microsoft 365 Roadmap for item ID 123456, which tracks the holiday file feature request.