Which calendar apps can open the file?

Any app that supports the iCalendar standard, including Google Calendar, Apple Calendar, Microsoft Outlook, and Thunderbird. The file follows RFC 5545, the format every major calendar imports.

How do all-day events work?

When you tick All day, the builder writes DTSTART and DTEND as a date value (VALUE=DATE) instead of a date-time. Per the standard, DTEND is the day after the last day, so a one-day event ends the following date.

What does the reminder do?

It adds a VALARM block with a DISPLAY action and a negative trigger such as -PT15M, which tells the calendar to alert you 15 minutes before the event starts.

How is recurrence stored?

As an RRULE line, for example FREQ=WEEKLY for a weekly repeat. You can also set how many times it repeats with COUNT, which caps the series at that number of occurrences.

Is my event data uploaded?

No. The .ics text is assembled entirely in your browser and the file is created locally, so nothing about your event is sent to a server.

ICS / iCal Event Builder

An ICS builder creates the standard calendar file that lets anyone add an event to their own calendar with one click. The .ics (iCalendar) format is defined by RFC 5545 and understood by Google Calendar, Apple Calendar, Outlook, and almost every other app. This free tool turns a simple form into a valid file, entirely in your browser.

How it works

The tool wraps a single VEVENT inside a VCALENDAR envelope and fills in the required and optional properties:

UID — a unique identifier so re-importing updates the same event instead of duplicating it.
DTSTAMP — when the file was created, in UTC.
DTSTART / DTEND — the start and end, as a UTC date-time (...Z) for timed events or a plain DATE for all-day events.
SUMMARY, LOCATION, DESCRIPTION — your text, with commas, semicolons, and newlines escaped as the spec requires.
RRULE — an optional recurrence rule like FREQ=WEEKLY;COUNT=8.
VALARM — an optional reminder with a TRIGGER such as -PT15M.

Long lines are folded at 75 octets with a leading space on continuation lines, and line endings use CRLF, both of which the standard mandates.

Tips and notes

Special characters in text are escaped automatically — you do not need to add backslashes yourself.
Keep the UID stable if you re-export an edited version, so calendars treat it as an update rather than a new event.
For all-day events remember DTEND is exclusive, so the tool sets it to the day after your chosen end date.
The generated file is plain text — open it in any editor to inspect exactly what your calendar will import.