  In the course of web research it is often necessary to estimate the creation
datetime for web resources (in the general case, this value can only be
estimated). While it is feasible to manually establish likely datetime values
for small numbers of resources, this becomes infeasible if the collection is
large. We present "carbon date", a simple web application that estimates the
creation date for a URI by polling a number of sources of evidence and
returning a machine-readable structure with their respective values. To
establish a likely datetime, we poll bitly for the first time someone shortened
the URI, topsy for the first time someone tweeted the URI, a Memento aggregator
for the first time it appeared in a public web archive, Google's time of last
crawl, and the Last-Modified HTTP response header of the resource itself. We
also examine the backlinks of the URI as reported by Google and apply the same
techniques for the resources that link to the URI. We evaluated our tool on a
gold-standard data set of 1200 URIs in which the creation date was manually
verified. We were able to estimate a creation date for 75.90% of the resources,
with 32.78% having the correct value. Given the different nature of the URIs,
the union of the various methods produces the best results. While the Google
last crawl date and topsy account for nearly 66% of the closest answers,
eliminating the web archives or Last-Modified from the results produces the
largest overall negative impact on the results. The carbon date application is
available for download or use via a webAPI.
