Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Q&A for work
Connect and share knowledge within a single location that is structured and easy to search.
On this Timeline on Patents.SE, for example, hovering over the S shows it stands for "simultaneous dates" (see image below).
This works on Chrome desktop, but not on Opera mobile.