Ordinary Time in the Liturgical Cycle
"Besides the times of the year that have their own distinctive character, there remains in the yearly cycle of 33 or 34 weeks in which no particular aspect of the mystery of Christ is celebrated, but rather the mystery of Christ itself is honored in its fullness, especially on Sundays. This period is known as Ordinary Time".
Ordinary Time begins on Tuesday, January 10th and continues through Tuesday, February 21st, the day before Ash Wednesday and the beginning of Lent. Ordinary Time resumes when the Easter season ends, that is Monday, the 29th of May, the day following Pentecost.