Import an ICS file to Office 365 calendar

Handed an ICS file of the year's project milestones and I want the events inside my Office 365 calendar proper, visible on phone and in every client.

Import versus subscribe keeps coming up. Which applies to a file and what are the steps?

A file means import: the events copy into your calendar once and become yours. Subscribe applies to ICS URLs, live feeds refreshing from a source and a file on disk has no source to refresh from. The import, browser route first since it lands server side by construction:

1

At outlook.office.com switch to the Calendar view.

2

Choose Add calendar in the left panel, then Upload from file.

3

Browse to the ICS, pick which of your calendars receives the events, your main calendar for phone visibility and Import.

4

The events appear throughout the account within minutes, phone included, as ordinary appointments you own, editable and deletable individually since the file connection ended at import.

Desktop Outlook imports the same file via File, Open and Export, Import an iCalendar file, with one attention point: the dialog offers Open as New alongside Import, and Open as New creates a separate temporary calendar rather than merging into yours, the classic where did my events go of this task. Recurring events in the file carry their recurrence rules through either route, and re-importing an updated version of the same file later duplicates rather than updates, the moment a genuinely maintained milestone list deserves promotion to a shared calendar or a subscribed URL instead of file passing.

Browser import into the main calendar and the milestones reached my phone before the meeting ended. The Open as New warning solved a colleague's mystery from last month too, her events were sitting in a temporary calendar all along.