Calendar basics -- Part I. Arithmetical calendars -- The Gregorian calendar -- The Julian calendar -- The Coptic and Ethiopic calendars -- The ISO calendar -- The Icelandic calendar -- The Islamic calendar -- The Hebrew calendar -- The Ecclesiastical calendars -- The Old Hindu calendars -- The Mayan calendars -- The Balinese Pawukon calendar -- Generic cyclical calendars -- Part II. Astronomical calendars -- Time and astronomy -- The Persian calendar -- The Bahai calendar -- The French Revolutionary calendar -- Astronomical Lunar calendars -- The Chinese calendar -- The Modern Hindu calendars -- The Tibetan calendar -- Part III. Appendices.