DayZ failed to meet its planned 2012 release date because creator Dean Hall was given the opportunity to make the mod into something much more.
Posting on the official DayZ Tumblr, Hall wrote: "I suppose I should start with the question everyone wants to know… where is DayZ Standalone? Obviously, it's not here. At Eurogamer [Expo] I said that DayZ had to be out before the end of the year and that's come and gone. I still stand by that comment, to achieve what we had originally wanted, we did have to be out by the end of the year - and we've failed to achieve that.
"Put simply, DayZ Standalone isn't here because we had the chance to go from making a game that was just the mod improved slightly, packaged simply, and sold - to actually redeveloping the engine and making the game the way we all dreamed it could be. This blew any initial plans we had dictated to pieces."
Progress is, however, being made.
"The plan from here is straightforward," continued Hall. "We will be releasing a closed test imminently, during which approximately 500-1000 people will assist in ensuring our architecture is correctly functioning. This closed test will be focused purely on architecture, not the game design. Once we have confirmed fixes for issues arising from the closed test, we will then reschedule an internal date for our public release."
The biggest change thus far implemented over the mod is a complete overhaul of the inventory system.
"The inventory and item management system was completely removed and rewritten from the ground by Jirka, one of the original engine programmers," explained Hall. "The work that has been completed on this groundbreaking, and it going to fundamentally change the DayZ experience.
"You scavenge for items now, as individual parts, picking up pieces rather than piles, looking for cans on shelves or under beds. The new system opens the door for durability of items, disease tracking (cholera lingering on clothes a player wears...), batteries, add-on components, and much more. If you shoot a player in the head to take his night vision, you will damage the night vision. The changes to this inventory system are huge."
In addition, a more intuitive 3D inventory has been created which features drag and drop-able 3D models rather than 3D pictures.
Work is also moving along very nicely on the game's art, including reworked textures to make them look "more post-apocalyptic".