This post describes Google Calendar CSV import format.

The first row of the CSV import file includes headers like “Subject” and “Start Date.” To import into Google Calendar, the headers must be in English. For the correct headers you need to import into Calendar, go to the list below.

Each row below the header row represents an event. For example:

Format headers & events in .csv files

Only the first 2 headers in this list are required. The rest are optional.

Important: The headers must be in English as shown in this article. If any event details have commas (like the location example given), you can include them with quotation marks around the text.

• Subject
  (Required) The name of the event
  Example: Final exam
• Start Date
  (Required) The first day of the event
  Example: 05/30/2020
• Start Time
  The time the event begins
  Example: 10:00 AM
• End Date
  The last day of the event
  Example: 05/30/2020
• End Time
  The time the event ends
  Example: 1:00 PM
• All Day Event
  Whether the event is an all-day event.
  • If it’s an all-day event, enter True.
  • If it isn’t an all-day event, enter False.
    Example: False
• Description
  Description or notes about the event
  Example: "50 multiple choice questions and two essay questions"
• Location
  The location for the event
  Example: "Columbia, Schermerhorn 614"
• Private
  Whether the event should be marked private.
  • If it’s private, enter True.
  • If it isn’t private, enter False.
    Example: True

These examples would create the following event:

• Event: "Final exam" on May 30, 2020 10:00 AM–1:00 PM
• Location: "Columbia, Schermerhorn 614"
• Description: "50 multiple choice questions and two essay questions"
• Private: Private event

source: Import events to Google Calendar - Computer - Google Calendar Help