As @DJClayworth said in the comments, these two stories are by different authors so I higlhy doubt they are connected.

• Both are recovering from an/the apocalypse

In The Hunger Games, they are recovering from a massive rebellion against the Capitol, so it's basically a "military apocalypse". In the Maze Runner, the apocalypse was caused by catastrophic solar flares followed by the Flare, which is a virus that killed millions.

• I think the Maze Runner events might be "the dark days" that President Snow was referring to in the Hunger Games

When President Snow refers to "the dark days", he refers to the war between the districts and the Capitol. There are absolutly no references to a virus or any pandemic at all in The Hunger Games.

• Everyone wears black that's a military person in the Maze Runner, like how the rebels wear black in The Hunger Games

This detail is pretty absurd to notice as a connection between the two stories in a way that almost all military person in stories (or real life) are often wearing black. It's just basic gear for military forces or rebels.

As @DJClayworth said in the comments, these two stories are by different authors so I higlhy doubt they are connected.

• Both are recovering from an/the apocalypse

In The Hunger Games, they are recovering from a massive rebellion against the Capitol, so it's basically a "military apocalypse". In the Maze Runner, the apocalypse was caused by catastrophic solar flares followed by the Flare, which is a virus that killed millions. So these are two different apocalypse with no link between them.

• I think the Maze Runner events might be "the dark days" that President Snow was referring to in the Hunger Games

When President Snow refers to "the dark days", he refers to the war between the districts and the Capitol. There are absolutly no references to a virus or any pandemic at all in The Hunger Games.

• Everyone wears black that's a military person in the Maze Runner, like how the rebels wear black in The Hunger Games

This detail is pretty absurd to notice as a connection between the two stories in a way that almost every military person or special force in stories (or real life) are often wearing black. It's just basic gear for military forces or rebels.