Why do Jehovah's Witnesses keep coming up with a date for the end times only to change it later?

They've been changing things for decades.  They call it "new light", like God is sending them 'updates' about everything from who he is, to calling the cross a "torture stake", to prophecies of the end of the world.  And the Watch Tower doesn't tell the upcoming JW's about what's been altered.  

Who told you that?  Jehovah’s Witnesses DO NOT keep coming up with dates concerning the end. 

We know from our study of the scriptures that the date is at Jehovah God’s discretion and nobody knows, not even his Son Jesus Christ.

The JWs are liars and so are their cult leaders.

Here's just a taste......"For over thirty years before that date and for half a century since, Jehovah's witnesses have pointed to the year 1914 as the time for the end of "the appointed times of the nations" and the time in which Christ would begin his Kingdom rule. (Luke 21:24)" Watchtower 1966 Feb 15 p.103"But bear in mind that the end of 1914 is not the date for the beginning, but for the end of the time of trouble." Zion's Watch Tower 1894 Jul 15 p.226"The beginning of the earthly phase of the Kingdom in the end of A.D. 1914 will, we understand, consist wholly of the resurrected holy ones of olden time-from John the Baptizer back to Abel;-"Abraham, Isaac, Jacob and all the holy prophets."" Studies In the Scriptures - The Day of Vengeance (1897) p.625"the deliverance of the saints must take place some time before 1914 is manifest" Thy Kingdom Come (1911 ed.) p.228"the Day of Vengeance ... will end in October, 1914" The Day of Vengeance p.547"the great "time of trouble such as never was since there was a nation," will reach its culmination" The Time Is at Hand (1889 ed.) page 77 - page 78"we present proofs that the setting up of the Kingdom of God is already begun" The Time Is At Hand (1889 ed.) p.101"we consider it an established truth that the final end of the kingdoms of this world, and the full establishment of the Kingdom of God, will be accomplished near the end of A.D.1914." Studies in the Scriptures - The Time is at Hand (1889) 1911 ed. p.99"October, 1914, will witness the full end of Babylon" Watch Tower 1911 Jun 15 p.190 (reprints p.4842)"Christendom, will have passed away, as already shown in prophecy." Thy Kingdom Come (1891 ed.) p.153Go to JW FACTS dot com for all of this cults lies.

Jehovah’s Witnesses have not given a date regarding the end of times. Why?  Because in the Bible Jesus says:  “Keep on the watch,+ therefore, because you know neither the day nor the hour.+” (Matthew 25:13) Therefore, JW do not speculate on dates and times but sound out the warning that the Bible says the end will come.  (Matthew 24:14)

I don't know where you're getting this info from. But Jehovah witnesses comply only with what the bible says. In the bible only God knows the hour or time when the end will come. Jesus said: “Concerning that day and hour nobody knows, neither the angels of the heavens nor the Son, but only the Father.”

However, Jesus did provide a composite “sign,” or group of events, that would identify the time period leading up to the end of the world. 

https://www.jw.org/en/bible-teachings/questions/en...

What else are they going to do? If they just said that it would happen 'soon' then drag it out for two thousand years, that would never work......or would it?

That classifies JW's as false prophets. Why anyone would attend a church service with a track record as theirs is beyond me. In Matthew 7:15, Jesus' words even warn of false prophets and the traits one might expect from them. Though JW's did not exist in Jesus' days on Earth, they sure do fit the description! 

Matthew 7:15-23

It’s a false prophet cult..

DUH

They're counting on their followers being too stupid to notice their record of 150 years of 100% bullsh*t 'predictions'.