For future reference, note that schematics are normally marked with positive and negative voltage inputs in the same way, regardless of which convention may be used for labelling current flow.It's called people need to use one system. One of the schematics I looked at for my 555 used electron flow and didn't specify that while the other used conventional.
It is rare to find electron flow indicated as current direction, but probably less rare for people to make mistakes in reading or writing schematics. You can never be too sure, particularly with things that come from sources whose credibility is uncertain, e.g. on the internet.
When it comes to IC pin-outs, checking against manufacturers' data sheets is a good idea, though not infallible. For a common device like the 555 it is often possible to cross-check with more than one supplier.