In addition to reforming (i.e., restoring) the church’s view on justification and salvation, the reformers diverted from the eschatology of the medieval period, returning the church to a more orthodox view of redemptive history. In the medieval period, a view took hold wherein the present age was seen as nothing more than an interlude, with no historic significance, between the two advents. In this way, the church was depicted as just pilgrims on a wayward journey. This changed significantly during the 16th century, when emphasis on the importance of the present age in God’s redemptive plan resulted in renewed interest in eschatology.
Martin Luther affirmed the orthodox Augustinian view of a visible second coming and a bodily resurrection and final judgment. He joined with the Roman Catholic Church in rejecting an earthly millennial kingdom. Of course he did have his eschatological differences with the Catholic Church, in that he identified Rome as the seat of the Antichrist. It is hard to say whether he should be considered amillennial or postmillennial, for (much like Augustine) he does not fit either term in the modern sense. We can just be sure (again, like Augustine) that Luther was not premillennial.
John Calvin’s eschatology is similarly nebulous, although there are found in his writings tenets of both modern amillennialism and postmillennialism. Like Luther, he identified Rome as the "see of the Antichrist." As for premillennialism, he wrote: "[it is] too childish to either need or be worth a refutation". He did favor a spiritual view of the Kingdom of God, which would place him in the amillennial camp. Yet he also looked forward to a sweeping success of the Great Commission, a central theme of postmillennialism.
The Westminster confession does not endorse amillennialism or postmillennialism (although it, like the creeds, implicitly rejects chiliasm (the 1000 year earthly kingdom). In answering the question regarding the second petition of the Lord’s prayer (Larger Catechism, Q191), many tenants of modern postmillennialism are evident, including the optimistic hope of a massive conversion of ethnic Jews2(I might be one of them, depending on how you define ethnic Jewishness):
Q. 191. What do we pray for in the second petition?
A. In the second petition, (which is, Thy kingdom come) acknowledging ourselves and all mankind to be by nature under the dominion of sin and Satan, we pray, that the kingdom of sin and Satan may be destroyed the gospel propagated throughout the world the Jews called the fullness of the Gentiles brought in; the church furnished with all gospel-officers and ordinances purged from corruption, countenanced and maintained by the civil magistrate: that the ordinances of Christ may be purely dispensed, and made effectual to the converting of those that are yet in their sins, and the confirming, comforting, and building up of those that are already converted: that Christ would rule in our hearts here, and hasten the time of his second coming, and our reigning with him forever: and that he would be pleased so to exercise the kingdom of his power in all the world, as may best conduce to these ends.
1 Much of this discussion comes from Postmillennialism, An Eschatology of Hope, Keith A. Mathison, P&R Publishing, 1999.
2 For scriptual references (proof texts) see this site.