There are many different interpretations of the 1000 years which the Apostle John saw in the Revelation.
However, they all agree that the 1000 years is a literal 1000 years. These interpretations do not allow for the probability that the number 1000 could be symbolic, as the rest of the Revelation is. In fact, by labeling the 1000 years as ‘the Millennium,’ it makes it even harder for one to realize this.
When one looks carefully at what John actually wrote about the 1000 years, as well as what did Jesus and his apostles taught, we begin to see that the 1000 years had its fulfillment in the time of the apostles.

The Events of the Revelation, including the ‘Millennium,’ were contemporary to John’s time

The angel instructed John that the events portrayed in the Revelation were about to take place. Not only that, these events would conclude in a short time.

In the very first chapter of the revelation, in the very first verse, John was informed that the vision was “to show to his servants things which must shortly come to pass; and he sent and signified it by his angel to his servant John…” (Revelation 1:1)

The directive continued in verse 3, specifying that “…the time is at hand.” (Revelation 1:3)
And just 8 verses later in the first chapter, again John was instructed to “write the things that you have seen, and the things that are, and the things that are about to take place after these…” (Revelation 1:19)

Clearly, Christ was very insistent that all the events of the Revelation, were either already occurring in John’s time, or were about to occur. John would be alive to witness their fulfillments. This would equally apply to the 1000 years, as well as the destruction of the Temple of Jerusalem.