Before that was the "base reality" which was hijacked and overwritten by GB and the Allies using German (reason behind WWII) and ancient Egyptian technology. A new simulation was created, a fake world to "experiment" imaginative scenarios. Everything happening in this world is coming right out of an agent's mind who now exists in the "base reality" in the late 1940's.

Major events in our fake world (timeline):

1947

Roswell
Creation of CIA, Mossad and Israel as proxies by Britain
Marriage of Queen Elizabeth II and Prince Philip

1952

Cairo Fire
Queen Elizabeth II assumes the throne
Ousting of the last Egyptian monarchy by Britain
Introducing the Multiverse theory for the first time

After that at the end of every decade, shifts occur in the simulation in which every decade (50's, 60's,70's, 80's 90's) is a discrete period with its own identity. Within those years, the simulation is paused, changes made and then resumed.

2000

The simulation is altered in which the years to follow will be experienced as one blob of time.

2001

September 11th

2010

The simulation is altered to prepare for world changing events.

The Mandela Effect term was coined according to current reality.

2011

Arab Spring

Fukushima

Building of the Grand Ethiopian Renaissance Dam which threatens the existence of Egypt and Sudan

2012-2013

Rise and fall of the Muslim Brotherhood

2015

The simulation is altered to prepare for world changing events. The changes can be noticed as many memories have not fully been rewritten. The Mandela Effect start spreading on the Internet.

2016

Donald Trump

2017

The simulation is altered to radically keep editing history. At the time of writing this post, Israel's capital Tel Aviv is now Jerusalem; according to current timeline history, it has always been Jerusalem and never been Tel Aviv (It has nothing to do with Jerusalem being accepted internationally as a capital or Tel Aviv being the political and cultural hub and the place for embassies). Many people remember Tel Aviv being the official capital of Israel.

To be continued ..