Start a Buried game by going to Zombies > Resolution 1295 > Processing > Buried
NOTE: This achievement DOES work on easy so if you're new to zombies try that!
Go down into the tunnels.
Find the blue glowing mystery box opposite the general store.
Keep hitting the box until you get the Time Bomb [950pts per try].
NB: In the higher rounds, if you lose the box you can find it by buying the vulture perk from the church [3000pts], however if you are solely going for this achievement I recommend simply restarting the game if you don't get it before the box moves.
The time bomb is used like C4. Press down on the dpad.
Throw the bomb with left trigger then when you wish, press right trigger to travel back to the time and place when/where you threw the time bomb.
Pop goes the cheevo.
Happy hunting
coreymawf
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All credit for this youtube video goes to Howess.