Per GitHub’s REST API v3 documentation for list commits on a repository:
GET /repos/:owner/:repo/commits
includes since and until parameters:
+--------+---------+---------------------------------------------------------------+
| Name | Type | Description |
+--------+---------+---------------------------------------------------------------+
| since | string | Only commits after this date will be returned. |
| | | This is a timestamp in ISO 8601 format: YYYY-MM-DDTHH:MM:SSZ. |
| until | string | Only commits before this date will be returned. |
| | | This is a timestamp in ISO 8601 format: YYYY-MM-DDTHH:MM:SSZ. |
+--------+---------+---------------------------------------------------------------+
For example, to select commits on master in June 2018 on github/linguist: https://github.com/github/linguist/commits/master?since=2018-05-31&until=2018-07-01
According to the above-linked docs, the branch should be included as a query parameter, e.g. https://github.com/github/linguist/commits?branch=master&since=2018-05-31&until=2018-07-01 but it seems to work fine to use the branch name as a path parameter.