That's fairly thin ice to be walking on. One could just as easily say one has to believe in fairy tales to think that biblical prophecy is valid.
It's fairly clear to somone who reads the Bible and knows what is going on around them.
Matthew 24:32-34
32 "Now learn this parable from the fig tree: When
its branch has already become tender and puts forth
leaves, you know that summer is near.
33 So you also, when you see all these things, know
that it is near--at the doors!
34 Assuredly, I say to you, this generation will by
no means pass away till all these things take place.
35 Heaven and earth will pass away, but My words
will by no means pass away.
Jesus gives the warning that we don't know the exact time -- but He also says we know the general time (or the season).
Matthew 24:36
36 "But of that day and hour no one knows, not even
the angels of heaven, but My Father only.
There are all sorts of subsequent warnings to be ready for Jesus Christ -- as He comes quickly and surprises people (those who think He's going to be a long time in the coming...)
Matthew 24:37-51
37 But as the days of Noah were, so also will the
coming of the Son of Man be.
38 For as in the days before the flood, they were
eating and drinking, marrying and giving in
marriage, until the day that Noah entered the ark,
39 and did not know until the flood came and took
them all away, so also will the coming of the Son of
Man be.
40 Then two men will be in the field: one will be
taken and the other left.
41 Two women will be grinding at the mill: one will
be taken and the other left.
42 Watch therefore, for you do not know what hour
your Lord is coming.
43 But know this, that if the master of the house
had known what hour the thief would come, he would
have watched and not allowed his house to be broken
into.
44 Therefore you also be ready, for the Son of Man
is coming at an hour you do not expect.
45 "Who then is a faithful and wise servant, whom
his master made ruler over his household, to give
them food in due season?
46 Blessed is that servant whom his master, when he
comes, will find so doing.
47 Assuredly, I say to you that he will make him
ruler over all his goods.
48 But if that evil servant says in his heart, 'My
master is delaying his coming,'
49 and begins to beat his fellow servants, and to
eat and drink with the drunkards,
50 the master of that servant will come on a day
when he is not looking for him and at an hour that
he is not aware of,
51 and will cut him in two and appoint him his
portion with the hypocrites. There shall be weeping
and gnashing of teeth.
And in yet another place, we notice that Jesus again talks about those who think He's coming later and are not ready.
Matthew 25:1-13
1 "Then the kingdom of heaven shall be likened to
ten virgins who took their lamps and went out to
meet the bridegroom.
2 Now five of them were wise, and five were foolish.
3 Those who were foolish took their lamps and took
no oil with them,
4 but the wise took oil in their vessels with their
lamps.
5 But while the bridegroom was delayed, they all
slumbered and slept.
6 And at midnight a cry was heard: 'Behold, the
bridegroom is coming; go out to meet him!'
7 Then all those virgins arose and trimmed their
lamps.
8 And the foolish said to the wise, 'Give us some of
your oil, for our lamps are going out.'
9 But the wise answered, saying, 'No, lest there
should not be enough for us and you; but go rather
to those who sell, and buy for yourselves.'
10 And while they went to buy, the bridegroom came,
and those who were ready went in with him to the
wedding; and the door was shut.
11 Afterward the other virgins came also, saying,
'Lord, Lord, open to us!'
12 But he answered and said, 'Assuredly, I say to
you, I do not know you.'
13 Watch therefore, for you know neither the day nor
the hour in which the Son of Man is coming.
Jesus warns that not knowing the day or hour -- does not mean to not know the times that you are in.
Luke 12:54-56
54 Then He also said to the multitudes, "Whenever
you see a cloud rising out of the west, immediately
you say, 'A shower is coming'; and so it is.
55 And when you see the south wind blow, you say,
'There will be hot weather'; and there is.
56 Hypocrites! You can discern the face of the sky
and of the earth, but how is it you do not discern
this time?
There will be those who say, "Oh He hasn't come in two thousand years, so He's not coming any time soon.
2 Peter 3:1-7
1 Beloved, I now write to you this second epistle
(in both of which I stir up your pure minds by way
of reminder),
2 that you may be mindful of the words which were
spoken before by the holy prophets, and of the
commandment of us, the apostles of the Lord and
Savior,
3 knowing this first: that scoffers will come in the
last days, walking according to their own lusts,
4 and saying, "Where is the promise of His coming?
For since the fathers fell asleep, all things
continue as they were from the beginning of
creation."
5 For this they willfully forget: that by the word
of God the heavens were of old, and the earth
standing out of water and in the water,
6 by which the world that then existed perished,
being flooded with water.
7 But the heavens and the earth which are now
preserved by the same word, are reserved for fire
until the day of judgment and perdition of ungodly
men.
The Apostle Pauls says that we know the time (we "are not in darkness, so that this Day should overtake ... [us] as a thief.")
1 Thessalonian 5:1-5
1 But concerning the times and the seasons,
brethren, you have no need that I should write to
you.
2 For you yourselves know perfectly that the day of
the Lord so comes as a thief in the night.
3 For when they say, "Peace and safety!" then sudden
destruction comes upon them, as labor pains upon a
pregnant woman. And they shall not escape.
4 But you, brethren, are not in darkness, so that
this Day should overtake you as a thief.
5 You are all sons of light and sons of the day. We
are not of the night nor of darkness.
We know that we will be "caught up" to be with the Lord in the air. The Apostle Paul says "Therefore comfort one another with these words."
1 Thessalonians 4:13-18
13 But I do not want you to be ignorant, brethren,
concerning those who have fallen asleep, lest you
sorrow as others who have no hope.
14 For if we believe that Jesus died and rose again,
even so God will bring with Him those who sleep in
Jesus.
15 For this we say to you by the word of the Lord,
that we who are alive and remain until the coming of
the Lord will by no means precede those who are
asleep.
16 For the Lord Himself will descend from heaven
with a shout, with the voice of an archangel, and
with the trumpet of God. And the dead in Christ will
rise first.
17 Then we who are alive and remain shall be caught
up together with them in the clouds to meet the Lord
in the air. And thus we shall always be with the
Lord.
18 Therefore comfort one another with these words.
The very last words in the Bible --
Revelation 22:20-21
20 He who testifies to these things says, "Surely I
am coming quickly." Amen. Even so, come, Lord Jesus!
21 The grace of our Lord Jesus Christ be with you
all. Amen.