LAST DAYS was a texture pack started by Doku (creator of the ever popular RPG pack). Doku began this pack with the essential land-scape defining textures (Dirt, Grass, Stone, water, trees, etc) but did not have time to do much more before discontinuing the pack.
In order to use HD texture packs properly (32× and higher) you will need to either patch your Minecraft using MCPatcher or using OptiFine. Optifine is preferred as it includes all of the features of MCPatcher, and greatly increases game speeds and graphics settings. MCPatcher tends to be updated on the same day as Minecraft updates, so use it instead if you are in a hurry.