[KarlInOhio]

No indication on how the date was established. Was it exactly 6,200 years ago, to the hour?

From the linked paper http://advances.sciencemag.org/content/2/9/e1501623.full

The earliest textiles decorated with blue at Huaca Prieta were excavated from stratum 44 in J. Bird’s HP-3 trench. Although not decorated with indigo, the earliest cotton yarn is from stratum 52, which is radiocarbon-dated at 6882–6657 cal BP [sample AA82121; see the study by Dillehay et al. (3)]. The next radiocarbon-dated level is stratum 35 at 5848–5585 cal BP (sample AA86948 on charcoal from an intact hearth), suggesting that the two textiles from stratum 44 are about 6200 to 6000 years old.

(BP = before present)

[sagar]

Do they do BP so that they can avoid using the BC Before Christ acronym?