The artifact, marked with ordered dots and strips that may well represent the lunar cycle, was found in Nguom Hau Cave (Na Hang District, Tuyên Quang province, Northern Vietnam).
A similar artifact was discovered in 1985 not far away: Na Cooc Cave (Thái Nguyên province).
The calendar has been estimated to be from c. 4000 years ago.
The stone tool was found in a tomb marked with 14 large stones laid at a length of 1.6m. Bones were found under the stones but no skull was found, with Chung guessing that the skull may have decayed due to the humidity in the cave.
A number of other stone tools were buried with the corpse.
The dig also produced much other information from the Iron Age (3.0-3.5 Ka BP), Late Neolithic (4.0-4.3 Ka BP) and a deeper and very thick Early Neolithic layer consisting of many polished stone axes and other tools.
Together with other findings, the evidence mounts for inhabitation from at least 8000 years ago in this area.