1967 the Jews retook Jerusalem back into their hands. It was a necessary requirement for bible prophecy to be fulfilled because Jerusalem has to welcome Jesus = saying blessed is he who comes in the name the Lord.
The parable of the fig tree is based on correctly identifying the fig tree. There is support in the bible for both Israel and Jerusalem being the fig tree.
Verses in the Tanach (old testament) support that Israel is the fig tree, and many commentators back before 2011 theorized that 1948 when Israel became a nation again that was the generation that would not pass without seeing Jesus's return.
So they took 1948 added 70 years for the length of a generation (Psalms 90) and came up with Jesus returning no later than 2018. The problem arose because there are the 7 years of the 70th week that must precede Jesus's return - which would have meant 2011 as the no later than start of the 70th week. Didn't happen. So that theory fizzled.
By the same process, but based on verses in the new testament on Jerusalem being the fig tree - specifically based upon Jesus cursing the fig on the side of the road, as representing Jerusalem, who would reject him as being her king.
So 1967 adding 70 years is the 2037, Jesus returning to earth no later than. And taking into account the 70th week preceding His Return - 2030 is the no later than deadline for the 70th week to begin.
Of course since 1967, Jerusalem has been the center of attention in dispute and conflict over, and we have to take into consideration that a temple will be built, of some sorts, on the temple mount in Jerusalem for a host of other major prophecies to take place during the 70th week.
So the 70th will have to start sometime between now and the end of 2030.
There are two preliminary prophecies to the start of the 70th week that must come first. 1st the formation of the ten leader form of Government of the EU with one leader over them, the little horn. 2nd, then the event of Gog/Magog must take place.