Why aren't we allowed to date? Why can't we get married to someone who isn't Orthodox? Is it a sin, and if yes, why?
Dating, especially at school age or early college life is in itself very much related to lack of maturity. It is a relation not in due time and not according to God's natural laws. Solomon the wise prophet said, "To everything, there is a season and a time to every purpose under the Heaven. A time to be born, and a time to die, a time to plant and a time to pluck up that which is planted, a time to weep and a time to laugh..." (Ecclesiastes 3:1-4)
Admiration and emotions which are biologically predominant at young age, are not enough to ensure a happy marital life. Compatibility, ability to compromise, integrity, sharing the same long range goals, and most importantly seeking a satisfying spiritual life together should be considered a priority in any relationship. This entails psychological development that surpasses the high school age and usually early college age. When a young couple reach the correct stage in life, that is after having finished their education, secured themselves jobs, then they can begin to think of marriage. Getting engaged, following parental agreement between both sets of parents, is the appropriate chance and time to get to know each other, each needs to discover a lot about the other, for example ways of thinking, interests, and lifestyle including spiritual maturity. Read the Holy Gospel of St. Luke 14:28-32 to learn about Our Lordís opinion concerning making major decisions in our lives. It requires that one should sit and reflect first on the consequences of his actions before taking a step that he might regret one day.
Boy-girl dating for pleasure is not Biblically documented. Marital relationships and raising a family should be taken very seriously.
An Orthodox Christian must marry in the Orthodox Church in order to achieve unity of the family, because the Lord taught that the two shall become one. This unity is unachievable in the absence of unity of faith. That is why both partners must be baptized Orthodox. If an Orthodox converts a non Orthodox prior to marriage, then this is called evangelism. If an Orthodox marries a newly baptized Orthodox, then it is the utmost responsibility of the former to encourage the latter to attend the Divine Liturgy on a regular basis and to teach him or her the principles of the Orthodox faith so that both partners may enjoy the full benefits of church life, and pass on these principles to their children.
Then this marriage will be like a house built upon THE ROCK. (Matthew 7:24-27)