I first noticed it on the Timeline for Winter Bash 2018 Knitting, but I've seen it on other timelines for other posts on other sites.
When I hover over certain events in the timeline:
- start of bounty,
- end of bounty,
- and suggested edit,
... the text of the timestamp becomes bold and a "S" appears to the left of the timestamp.
When I hover over the
S that has appeared, a tooltip shows up with text "simultaneous dates".
When I move the mouse away, it reverts to normal.
What is the purpose of this? Does this occur on any other timeline events? Is it just to indicate that those events occurred simultaneously?