KazakHD

As we know, half-life is the time in which half of radioactive isotops will decay. For example, for ²³²U (uranium 282) it takes 68.9 years to loose half of it's mass. That's the²³²U's half-life.

Now let's think about Half-Life series. Valve was found in 1996, HL was released in late 1998. Half-Life² was released in late 2004. Shouldn't we think mathematically?
If half-life for an element is 2 years, then half-life² for that element is 4 years (half-life*half-life=2*2).
If Valve was found in 1996 and Half-Life (which is equal to Half-Life¹) was released in late 1998, than it took at least 2 years to develop Half-Life.
6 years after HL1 release Half-Life² was released, so, let's find a quad root of Half-Life². SQRT(6)=2,44... Did it take 2.44 years to develop Half-Life¹? It's pretty close to the real data. And what happens if we literally count Half-Life³?
2,44^3=2,44*2,44*2,44=14,5 years. Let's take HL2 release date (late 2004 = 2004.8) and add 14,5 years which are equal to Half-Life³ - we get 2019. Now you know the release date :)

P.S.: To get more accurate results, it's better to count days instead of years, which I'm going to do later.
P.P.S.: Please, if you re-post this info, don't forget to give link to this blog! Thanks!