Ash Wednesday and Lent
The development of Ash Wednesday is closely tied to the development of Lent and Holy Week. The earliest observances of Easter were preceded by a few days of fasting, the actual number of days varying from place to place. Quite independently of the pre-Easter fast, there grew up in Egypt in the late fourth century a custom of keeping a forty day fast. This originally had nothing to do with Easter and was in imitation of Jesus’ own fasting. There was a wide-spread custom in the early church of fasting on Wednesdays and Fridays around the year. Lent was an extension of this to the other days of the week, except Sunday, for the forty day period. The development of the catechumenate by the fourth century meant that Lent became an ideal time for instruction in the faith, for sharing in the prayer of the church, and for the reconciliation of penitents, as well as for fasting. The desire to prepare thoroughly for the Easter festival met up with the observance of Lent to produce the Lenten season as we now have it. 
In the fourth century in Rome, Lent began on the fortieth day before the Easter sequence. By including the fast days of the Easter preparation, and by counting only actual days of fasting, it became the custom to begin the fast on the Wednesday before the sixth Sunday before Easter Day to give exactly forty days. Thus, by the early sixth century, Lent began on this Wednesday. Accounts of the observance of Ash Wednesday in Rome in the eighth century point to a spiritualised interpretation of putting on sackcloth and ashes. Ashes were a very ancient sign of repentance or mourning and were quite common in private use among early Christians. It was in the Rhine valley that the liturgical rite of the imposition of ashes developed. The custom spread, and was prescribed for all Christians at the Council of Benevento in 1091. It is common for the palms from the previous year’s Palm Sunday to be used to make the ashes.
By a process of further extension of the preparation for Lent, there developed in the sixth century the three Sundays before Lent, Quinquagesima, Sexagesima and Septuagesima, being (approximately) fifty, sixty and seventy days before Easter respectively.
Lent is a long period of fasting. In the western church there grew up the custom of some relaxation of the fast, particularly in connection with the fourth Sunday in Lent. It has had various titles. In England it was often called Mothering Sunday. Several reasons have been offered for this: that it comes from the custom of visiting one’s mother on this day; that it comes from the practice of visiting the mother church of the diocese (the cathedral) on this day; that it comes from the traditional Epistle reading with its reference to “Jerusalem . . . which is the mother of us all.” Not all revised Anglican Prayer Books have retained the observance. The custom of eating simnel cakes on this day (a rich fruit cake with almonds), comes from one of the other names for the day: Refreshment Sunday. 
Customs associated with the last week of Lent, Holy Week, owe their origin to the liturgical developments in Jerusalem. Egeria in the late fourth century testified to the custom developed in Jerusalem of acting out liturgically the events of Jesus’ last week in Jerusalem, beginning with his triumphal entry to the city. This is the origin of the Palm Sunday procession. The custom gradually spread throughout the church. In some places, other specific events from that week are associated with particular days. In A New Zealand Prayer Book - He Karakia Mihinare o Aotearoa, the Monday of Holy Week is associated with the Cleansing of the Temple, Tuesday with Teaching in the Temple, and Wednesday with the Anointing at Bethany (pp. 582 - 584).
For Liturgical Use
It has been a very long tradition of the church to call its members to a period of prayer, fasting, instruction and penitence, in preparation for the festival of Easter. Ash Wednesday marks the beginning of Lent. You are invited to use this period of forty days to deepen your faith and commitment to the way of God in Christ. Ash is an ancient symbol of penitence and humility. In a spirit of true Christian obedience let us keep this Ash Wednesday.
Sentence, Prayers and Readings as in A New Zealand Prayer Book - He Karakia Mihinare o Aotearoa, page 573-574.