Add to calendar (.ics file)

An .ics file is not a calendar: it is the envelope

When somebody sends you a date inside a message, that date goes nowhere: it sits there, and whoever receives it has to copy it out by hand. The .ics file is the format every calendar understands, and has since 1998: you attach it to an email, drop it in a chat, put it on a website, and whoever opens it finds the event already inside their own calendar, with the place, the notes and the reminder. It works on iPhone, on Android, in Outlook, in Google Calendar and in Thunderbird, because none of them has a format of its own that the others cannot read.

Here the file is written inside your browser and goes nowhere: the page has no server to send it to, so your home address, the client's name or the time of the appointment pass through nobody. If what you need is the opposite move, looking at a file your phone already knows without importing it into your contacts by mistake, the page is Open a .vcf address book.

The mistake that makes a one-day event take up two

It is the most famous trap in this format, and it only shows up later, on the phone of whoever receives it. In an all-day event the end date is exclusive: it is not the last day of the event, it is the day after. An event on the 4th of September is written «starts on the 4th, ends on the 5th», and whoever writes «starts on the 4th, ends on the 4th» ends up, depending on the program, with an event two days long or with an event that does not show at all.

Here the page does that sum for you: you write the first and the last day as you would say them out loud, and the day after is what lands in the file. It is also one of the things the test checks by reading the finished file back with programs written by other people, because on a rule like this a slip does not show on screen: it shows three weeks later, when somebody turns up on the wrong day.

Why the time zone is written out in full inside the file

«At three» means nothing if the reader is in London or in New York. A file made properly does not only write the hour: it also writes which zone that hour belongs to and how daylight saving works in that zone, with the exact dates of the two changes. A file that names the zone without explaining it is the typical breakage: every program copes its own way, and the appointment lands an hour later for half the people invited.

The rules do not come from a table written in here, which would go stale: they are asked of the browser, which carries the time zone database updated along with the system. There is one case worth knowing about, and it is the two nights when the clocks move: half past two on the night of the spring change does not exist, and half past two on the autumn night happens twice. If you pick an hour like that, the page tells you instead of writing a date that everybody will read their own way.

Twenty deadlines from a spreadsheet, and the things not done here

The second tab at the top is the one that earns its keep: you paste the rows of a spreadsheet, one per event, and out comes a single file with all the events inside. The format is date, time, title, place, and the time can be left out: a row with no time becomes an all-day event, which is exactly what a deadline needs. Copying from Excel brings the columns in separated by tabs, and they are recognised on their own; rows that cannot be understood do not quietly disappear, they get listed.

The things not done here are three, and each has its own page. No date is worked out: if you need to know where a ninety-day deadline falls there is Add days to a date, if you want to look at a whole month there is Monthly calendar, and if what you want is the countdown to the big day there is Event countdown. Dates written in prose, like «next Thursday at three», are not read, because guessing them wrong is worse than not trying. And invitations with a guest list are not sent: this is a file you open, not a summons. If you work shifts and your dates are already in a table, the place to come here from is Shift calendar.