Title, location, date and time, time zone, repeat, invitees, alerts, and notes — then download the .ics file or open it straight in your calendar. You can also paste a schedule or attach a document or photo to make several events at once.
How do I add a reminder or alert to an .ics event?
A reminder is a VALARM block inside the event: ACTION:DISPLAY for an on-screen notification, and TRIGGER:-PT30M for the offset, where PT introduces an ISO 8601 duration and the leading minus makes it fire before the start rather than after it. ICS Maker offers alerts from the form and writes one VALARM per alert, always spelling the offset in minutes — a day before is -PT1440M. An event may carry up to ten alarms here, but whether they all arrive is the reading calendar's decision: some add their own default alongside, and some strip alarms from imported events entirely so that a downloaded file cannot schedule notifications on a device.
The block it writes
BEGIN:VALARM
ACTION:DISPLAY
DESCRIPTION:Reminder
TRIGGER:-PT30M
END:VALARMA VALARM sits inside the event rather than beside it, so it travels with it. ACTION:DISPLAY is a notification on screen — the one every calendar supports. The alternatives, AUDIO and EMAIL, are far less portable: EMAIL in particular asks the reading calendar to send mail, which most simply decline to do.
Reading the trigger
TRIGGER:-PT30M is a duration, not a time, and the minus sign is what makes it before the event — a positive one fires after the start, which is occasionally what you want for a follow-up. The letters are an ISO 8601 duration: PT introduces a time, so PT30M is thirty minutes, PT2H two hours, and P1D a day. This builder always spells the offset in minutes — a day before is -PT1440M rather than -P1D, which is the same duration and marginally less likely to meet a fussy parser.
A trigger can also be tied to the end (TRIGGER;RELATED=END:-PT15M, a quarter of an hour before the meeting is due to finish) or given an absolute moment instead of an offset. Both are hand edits to the downloaded file; the form offers offsets from the start, which is what nearly every reminder is.
Several alerts, and whether they survive
An event may carry as many alarms as you like — a week ahead to prepare, an hour ahead to travel, five minutes ahead to join the call — and each is its own block. Whether they all arrive is up to the calendar that opens the file: a reminder is part of the event, but a calendar with its own default notifications may add one of its own alongside, and some strip alarms from imported events entirely rather than let a file schedule notifications on your phone. Check the first event after an import before trusting a batch of them.
Questions
- How do I set a reminder 15 minutes before an event?
- Choose it from the alert list before downloading, and the file gets a VALARM whose trigger is -PT15M. The minus sign means before the start; the calendar that opens the file schedules the notification itself.
- Can one event have more than one reminder?
- Yes. RFC 5545 puts no limit on the number of VALARM blocks inside an event, and adding a second alert here writes a second block; ten is the ceiling this builder enforces. A day-ahead and a ten-minutes-ahead pair is the common combination.
- Why did my reminder not appear after importing the file?
- The reading calendar decides. Some apply their own default notification to anything imported, some keep the file’s alarms, and some ignore imported alarms as a matter of policy so that a downloaded file cannot schedule notifications on your device. Open the event after importing and check the alert field before sending the file to anyone else.
- What does TRIGGER:-PT1H mean?
- One hour before the event starts. PT introduces a time-of-day duration in ISO 8601, 1H is one hour, and the leading minus makes the offset run backwards from the start. Without the minus it would fire an hour after the event began.