Morning Prayer is designed to sanctify the morning, as is clear from many of its parts. Saint Basil the Great excellently described the character of morning prayer in these words:

Matins consecrates to God the first movements of our minds and hearts; no other care should engage us before we have been moved with the thought of God, as it is written, "I thought of God and sighed" (Ps 76:4), nor should the body undertake any work before we have done what is said, "I say this prayer to you, Lord, for at daybreak you listen for my voice; and at dawn I hold myself in readiness for you, I watch for you" (Ps 5:4-5)

This Hour, recited as the light of a new day dawns, recalls the resurrection of the Lord Jesus, the true light, enlightening every person (cf John 1:9), 'the Sun of Justice' (Malachi 4:2), 'arising on high' (Luke 1:78).  Thus the remark of Saint Cyprian may be well understood:

We should pray in the morning to celebrate the resurrection of the Lord with morning prayer.

(From the General Instruction on The Liturgy of the Hours)

Evening Prayer is celebrated in the evening when the day is drawing to a close, so that 'we may give thanks for what has been given us during the day, or for the things we have done during it'. 

We also call to mind our redemption, through the prayer we offer 'like incense in the sight of the Lord', and in which 'the raising up of our hands' becomes 'an evening sacrifice'.  This 'evening sacrifice' 'may be more fully understood as that true evening sacrifice which was given in the evening by our Lord and Saviour when he instituted the most holy mysteries of the Church at supper with his apostles; or which on the following day he offered for all time to his Father by the raising up of his hands for the salvation of the whole world'.

Placing our hope in that Sun which never sets, 'we pray and beg that his light may shine on us again; we pray that Christ may come bringing the grace of eternal light'.

Finally, in this Hour, we join with the Eastern Churches and invoke blessed Jesus Christ, the Light of our Heavenly Father's sacred and eternal glory; as the sun sets we behold the evening light and sing to God, Father, Son and Holy Spirit ...'

(From the General Instruction on The Liturgy of the Hours)