vCalendar is an older standard exchange format for calendar information promulgated per Internet Mail Consortium (IMC). iCalendar is a newer standard (RFC 2445) for calendar information, heavy according to vCalendar.

On this button is an lesson of reference around vCalendar format: BEGIN:VCALENDAR PRODID:-//Ximian//NONSGML Evolution Calendar//EN VERSION:2.0 METHOD:PUBLISH BEGIN:VTIMEZONE TZID:/softwarestudio.org/Olson_20011030_5/Europe/Helsinki X-LIC-LOCATION:Europe/Helsinki BEGIN:DAYLIGHT TZOFFSETFROM:+0200 TZOFFSETTO:+0300 TZNAME:EEST DTSTART:19700329T030000 RRULE:FREQ=Annually;INTERVAL=One;BYDAY=-1SU;BYMONTH=3 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:+0300 TZOFFSETTO:+0200 TZNAME:EET DTSTART:19701025T040000 RRULE:FREQ=Every year;INTERVAL=I;BYDAY=-1SU;BYMONTH=10 END:STANDARD END:VTIMEZONE BEGIN:VEVENT UID:20030821T212557Z-2393-500-One-2@somehost.lesson.com DTSTAMP:20030821T212557Z DTSTART;TZID=/softwarestudio.org/Olson_20011030_5/Europe/Helsinki: 20030818T100000 DTEND;TZID=/softwarestudio.org/Olson_20011030_5/Europe/Helsinki: 20030818T113000 SUMMARY:foo SEQUENCE:1 Survive-MODIFIED:20030821T212558Z END:VEVENT END:VCALENDAR

Understand as well vCard.