New Liturgical Day

With the reading of the evening prayer "Vouchsafe, O Lord . . ." the transition to a new liturgical day is complete. Since the prayer is not read in the course of the Liturgy of the Presanctified or at the service of Vespers with Divine Liturgy, the transition to a new liturgical day is not complete until the conclusion of those services. Therefore the Presanctified or the Divine Liturgy is reckoned with the day that is ending and not with the one that is beginning.

But since the hymns sung at "Lord, I Call" belong (with some exceptions) to the new liturgical day and not to the day drawing to a close, the transition to a new liturgical calendar day has already begun well before the evening prayer "Vouchsafe, O Lord."

The structure of daily vespers from the evening prayer to the end of the service, exactly parallels the structure of daily matins from the same words ("Vouchsafe, O Lord . . .") where they occur in the small doxology, to the end of that service:

At daily vespers
At daily matins
Vouchsafe (Evening prayer)      
Litany: Let us complete ...
           
Aposticha                                   
Scripture song (Song of Symeon)
Trisagion prayers                       
Dismissal Troparia                     
Litany: Have mercy on us...      
Wisdom! Bless!                          
Christ our God ...                     
Amen.  Preserve, O God ...       
Most holy Theotokos, save us!   

More honorable ...                      
Glory to You ...                           
etc.  
                                   
        
Vouchsafe (in small doxology)
Litany: Let us complete ...
Aposticha
Scripture song (Psalm: It is good ...)
Trisagion prayers
Dismissal Troparia
Litany: Have mercy on us...
Wisdom! Bless!
Christ our God ...
Amen.  Preserve, O God ...
Most holy Theotokos, save us!
More honorable ...
Glory to You ....
etc.