On Monday, February the 19th 2018, will begin the blessed period of Great Lent. This is a period of strict fast* in the Orthodox Chuch, thus preparing us for the upcoming Holy Passion of Christ and His glorious Resurrection. During Great Lent, the daily cycle of services differ from that of the rest of the year. Vespers are celebrated daily in the morning accompanied by the Presanctified Divine Liturgy. The Great Compline is read every evening, instead of the Small Compline. The latter is only read every Friday night accompanied by the Akathist Hymn to the Theotokos, beginning on the first Friday of Lent until the fifth Friday. On Sundays we celebrate the Divine Liturgy of Saint Basil the Great instead of the one of Saint John Chrysostom which is usually celebrated throughout the rest of the year.
* the fast consists of abstinence from meat, meat products, fish, dairy products, oil and wine from the 19th of February 2018, Clean Monday, until Holy Pascha on April the 8th 2018.
Oil and wine is permitted on Saturdays and Sundays and fish is permitted on the 25th of March, feast day of the Annunciation of the Theotokos.
However, these are general fasting guidelines set by our Church Fathers, everyone must consult with their own spiritual father for their personal fasting rule.