From the Gelasian Sacramentary (7th Century) until the calendar reforms of Vatican II, the ninth Sunday before Easter was called “Septuagesima”, and the eighth Sunday before Easter (this year, this coming Sunday, 4 February 2018) was called “Sexagesima”. The third Sunday in this sequence, the last Sunday before Ash Wednesday (starting Lent), was Quinquagesima.
Sexagesima was a term already used in the Fourth Council of Orleans in 541. The Ordo Romanus, Alcuin, and others count the Sexagesima (60 days) from this day to Wednesday after Easter.
It interests me that, prior to the Vatican II reforms, from Septuagesima right through up to (but not including) the Last Sunday after Pentecost (the Sunday next before Advent) – that whole block of at least 40 Sundays in the church year (I think I’ve got that right!) were linked and moved with the date of Easter. And underneath and behind that this block of at least 40 Sundays with their set collect, introit, readings etc. were, hence, possible links back to the Jewish calendar.
Traditionalist Catholics and Lutherans continue this sequence.
Since Vatican II, the Church Year was re-designed. Now, rather than moving with Easter, Sundays in Ordinary Time stay close to a date in the Solar Year. For example, this coming Sunday, Ordinary 5, is always between 4-10 February.
There is nothing “ordinary” about “Ordinary Time”. Ordinary Time is not about common, regular, mundane, or run of the mill. Ordinary Time comes from the word “ordinal” as in “ordinal numbers”. Remember your Maths: Cardinal numbers answer “how many?” “Ordinal Numbers” tell the rank, they answer “what position?” Ordinal Numbers are first, second, third, fourth, etc.
There are normally fifty-two weeks in a year. These are made up of the Advent, Christmas, Lent, and Easter Seasons. Normally that leaves thirty-four weeks of “Ordinary Time”. Those weeks start from The Baptism of the Lord up to Lent, and start again at the Day of Pentecost.
If you are interested, read more about Ordinary Time here.
New Zealand’s Anglican Lectionary booklet jumps from the “4th Sunday of the Epiphany” to the next week being the “5th Sunday in Ordinary Time” – with no explanation of why it starts on the 5th Sunday and not the 1st Sunday in Ordinary Time. It calls the same Sunday “Proper 1” – again with no explanation that I can spot.