Valve began 2015 in style, hitting a new record high for Steam with 8.47 million concurrent users on Jan. 1, according to the service's stats page.
A graph on the page shows a peak of 8,466,441 concurrent users at 12:01 p.m. yesterday. (It's unclear what time zone the graph is using; we've reached out to Valve for clarification, and will update this article with any information we receive.) You can see a screenshot below of the graph with the peak marked.
Steam first hit 8 million concurrent users on June 29, 2014, the encore day of the year's Steam Summer Sale. The service topped 7.5 million back in December 2013, shortly after Christmas.