One month passed after Dean made his own dagger. One month and one week, roughly, since he fell on that place and needed to start to adventure inside the cave.
Anyway, Dean wasn't aware of that. He couldn't know how much time passed exactly. In his counts, it had been only three weeks in total but he wasn't sure.
Dean started to count the days he spent inside the cave just after he began to seriously hunt. However, without sunlight, he could only determine whether a day passed or not after he slept.
For a while, his body was still used to sleep some hours before the extended night of the apocalypse ended and the sun raised. That schedule was craved in his body because of the various months that he passed traveling with Rick and his group.
