Data collected from bitcoin core, for example:

On 30 October 2015 bitcoin core version updated from 0.10.2 to 0.11.1

On 23 February 2016 bitcoin core version updated from 0.11.2 to 0.12

On 16 May 2016 bitcoin core version updated from 0.12 to 0.12.1

On 10 November 2016 bitcoin core version updated from 0.13 to 0.13.1