The Celtic calendar is a compilation of pre-Christian Celtic systems of timekeeping, including the Gaulish Coligny calendar, used by Celtic countries to define the beginning and length of the day, the week, the month, the seasons, quarter days, and festivals.

The Gaulish Coligny calendar is possibly the oldest Celtic solar/lunar ritual calendar. It was discovered in Coligny, France, and is now on display in the Palais des Arts Gallo-Roman museum, Lyon. It dates from the end of the 2nd century CE., when the Roman Empire imposed^{[citation needed]} use of the Julian Calendar in Roman Gaul. The calendar is made up of bronze fragments, in a single huge plate. It is inscribed in Gaulish with Latin characters and uses roman numerals.

The Coligny Calendar is an attempt to reconcile both the cycles of the moon and sun, as is the modern Gregorian calendar. However, the Coligny calendar considers the phases of the moon to be important, and each month always begins with the same moon phase. The calendar uses a mathematical arrangement to keep a normal 12 month calendar in sync with the moon and keeps the whole system in sync by adding an intercalary month every 2½ years. The Coligny calendar registers a five-year cycle of 62 lunar months, divided into a "bright" and a "dark" fortnight (or half a moon cycle) each. The months were possibly taken to begin at full moon, and a 13th intercalary month was added every two and a half years to align the lunations with the solar year.

Mariah Carey (born March 27, 1970) is an American singer, songwriter, record producer, and actress. She made her recording debut in 1990 under the guidance of Columbia Records executive Tommy Mottola, and released her self-titled debut studio album, Mariah Carey. The album went multi-platinum and spawned four consecutive number one singles, on the U.S. Billboard Hot 100 chart. Following her marriage to Mottola in 1993, a series of hit records, including Emotions (1991), Music Box (1993) and Merry Christmas (1994), established her position as Columbia's highest-selling act. Daydream (1995), made music history when the second single, "One Sweet Day" a duet with Boyz II Men, spent a record sixteen weeks on top of the Billboard Hot 100, and remains the longest running number one song in US chart history. During the recording of the album Carey began to deviate from her pop background, and slowly traversed into R&B and Hip-hop. After her separation from Mottola, this musical change was evident with the release of Butterfly (1997).