From a Co-Worker letter dated Jan. 20, 1977,  by Herbert W. Armstrong:  

Just HOW does the BIBLE count a GENERATION?
 
     In counting successive generations in a genealogy (as of Christ),
it counts a generation from one's birth to the date of birth of his
son (as in Matt. 1:17).  But in speaking of an entire generation --
like this or that generation, it refers to the entire LIFE-time of
a generation, from birth to death.  For example, of the generation
then living in Moses' day, none of that entire generation then
living -- from 20 years and above -- was to be allowed to enter the
promised land.  They were 40 years in the wilderness.  So that
generation was at least 60 years.  The present living generation is
probably longer.
 
     So UNDERSTAND!  Jesus came with the GOSPEL (GOOD NEWS) ANNOUNCING the future coming of the KINGDOM OF GOD, immediately after He had QUALIFIED to replace the former super archangel Lucifer (Satan) on the throne at that time.
 
     The first man, Adam -- father and progenitor of the human race --  rejected the GOVERNMENT OF GOD, which Lucifer before him had rejected.  Adam made the decision to DECIDE FOR HIMSELF what is good and what is evil -- right and wrong -- rejecting God's LAW of God's government which defines what is right and what is wrong.  Adam deliberately CUT HIMSELF AND HIS HUMAN FAMILY OFF FROM GOD, AND ALL CONTACT WITH GOD.
 
     God compelled Adam to make his own decision.  Since he cut
himself off from God's government and all contact with God, the
Master Plan of God called for a 7,000-year period of which the
first seven days of creation in Genesis 1 were a type.  Six
millennial days (6,000 years), for man to run his course, going his
own way, cut off from God -- devising and building his own society,
civilization, and all in it.  Man had put himself under the sway
of Satan.  Satan shall remain on that throne of the earth UNTIL a
successor has qualified, AND HAS BEEN INDUCTED INTO OFFICE.
 
    So man, under the invisible sway of Satan, deceived into
believing Satan does not exist, established his own GOVERNMENTS, his own systems of education, his own systems of commerce and industry, his entire society with all its customs, and varied and various ideas of what is right and what is wrong.  God knew that it would take 6,000 years for man to bring himself to the point of DESTROYING HIMSELF -- of erasing all humanity from earth.  But just before that could happen, God will intervene.
 
    Now Jesus came over 1,900 years ago.  He ANNOUNCED the Kingdom of God -- to rule ALL NATIONS of the ENTIRE EARTH with the GOVERNMENT OF GOD -- which Lucifer had rejected -- and which, in turn, ADAM had rejected for the HUMAN FAMILY.  For 6,000 years God adopted a "hands-off" policy toward humanity -- except He reserved the right to INTERVENE on certain specific occasions which He deemed necessary for His PURPOSE.  He intervened in the incident of Cain slaying Abel.  Enoch walked with God -- lived GOD'S WAY.  God intervened with Noah and the Flood.  He intervened in the personal lives of Abraham, Isaac, Jacob and Joseph.  He intervened in the case of the nation ISRAEL -- but never promising them any spiritual blessings, salvation, or eternal life.  And He sent CHRIST with the GOOD NEWS, announcing almost 2,000 years in advance, the RESTORATION of the GOVERNMENT OF GOD, in the form of the KINGDOM OF GOD, to restore PEACE, happiness, and this time, SPIRITUAL SALVATION WITH ETERNAL.  LIFE for all who will obey His
laws.
 
    All this while -- from Adam -- GOD HAD NOT CALLED THE PEOPLES OF THE WORLD TO SALVATION and the gift of eternal life -- except those mentioned, and the prophets.
 
    Jesus said plainly, "None CAN COME to me except the Father draw him."  GOD WAS NOT TRYING TO SAVE THE WORLD OF HUMANITY -- YET!  But Jesus raised up HIS CHURCH -- THE CHURCH OF GOD.  They were specially called -- PREDESTINATED.  The Father did now draw those called to
salvation -- the VERY FEW.  Once called, it was THEIR PERSONAL CHOICE whether they accepted the call.
 
    WHY did He call a FEW -- and WHY only a few?  They were called to OVERCOME SATAN and Satan's world, even as Jesus did, TO QUALIFY TO SIT WITH HIM ON HIS DAVIDIC THRONE IN JERUSALEM, even as He had to overcome Satan to qualify to sit on this throne.  But ONE THING MORE -- VASTLY IMPORTANT -- they were called to HELP and STAND BACK OF
GOD'S CHOSEN APOSTLES in PROCLAIMING THE GOSPEL (GOOD NEWS) OF THE COMING KINGDOM OF GOD!
 
    But before 70 A.D. (Gal. 1:6-7; II Cor. 11:4; Rom. 1:18,25)
Jesus' Gospel ANNOUNCEMENT was SUPPRESSED, replaced with a "gospel" that DID AWAY with the Kingdom of God (calling it the church), did away with being born of God (the Trinity doctrine), and did away with God's law, thus leading a deceived world into SIN.
 
    But by 1927 we had REACHED THE VERY GENERATION WHEN MAN'S 6,000 years cut off from God will be concluded.  During this generation -- within 60 to 90 years OR LESS -- from 1927 -- CHRIST WILL COME AGAIN and RESTORE the GOVERNMENT OF GOD over the entire earth.  The dead IN CHRIST shall be resurrected immortal SPIRIT BEINGS -- we who are Christ's still then alive will be INSTANTLY CHANGED to immortality -- and WE SHALL REIGN OVER ALL NATIONS for 1,000 years!
 
    The GENERATION had come during which the happy WORLD TOMORROW, ruled by Christ and the KINGDOM OF GOD (YOU AND ME) will RESTORE PEACE AND HAPPINESS.
 
    SO -- the time had come when God WANTED THAT ANNOUNCEMENT -- that GOOD NEWS of the true Gospel -- TO GO TO all the WORLD of the generation when it will happen.    (END OF EXCERPT)