Fill in an event, or several, and download one .ics file that Google Calendar, Apple Calendar, Outlook and Thunderbird can import. Each event can have a time zone, an all-day date range, a repeat rule (daily, weekly on chosen days, monthly on a date or on "the 2nd Tuesday", yearly; every N; ending after a number of times or on a date), reminders, a location, a link, a description, an organizer and attendees. You can import a list of events from CSV, see the next ten occurrences of a repeating event, and open the event pre-filled in Google Calendar or Outlook on the web. The file is built in your browser; nothing is sent anywhere.
A correct file, by the standard
The output follows RFC 5545, the iCalendar specification, in the details that make or break an import:
- Line endings and folding. Lines end with CRLF and are folded at 75 octets (bytes, not characters) with a line break and a space. Vietnamese letters take 2 or 3 bytes in UTF-8 and emoji 4, so the tool folds between characters and never splits one in half, which is what turns "Họp" into "H�p" in careless generators.
- Escaping. Commas, semicolons and backslashes in titles and descriptions are escaped, and line breaks become
\n, so "Phòng 3, Tầng 5" stays one location. - Identity. Every event gets a unique UID and a DTSTAMP, so importing an updated file replaces the event instead of duplicating it.
- All-day events use dates only, and their end date is the day after the last day, as the standard requires.
Repeats without surprises
The repeat rule (RRULE) is written in the form the standard requires: UNTIL in UTC when the event has a time zone, as a date for all-day events, and inclusive of the last date you pick. Some combinations do less than people expect, and the occurrence list shows it before you send the file: "monthly on the 31st" skips the months without a 31st, a yearly event on 29 February appears only in leap years, and "the last Friday" differs from "the 4th Friday" in months with five Fridays.
Add-to-calendar links
The Google Calendar link uses Google's documented template parameters (title, dates, time zone, details, location and the repeat rule). The Outlook links work for personal (outlook.com) and work (Microsoft 365) accounts but are not an official API and cannot carry a repeat rule. Links are handy for one event on a web page; the .ics file is better for several events, reminders and attendees.
For the pitfalls behind invitations that arrive an hour off, read how calendar invites and .ics files work. To check a time in another city, use the time zone converter; to count days between two dates, the date calculator.
