Update ERRATA.md

[evanp]

The startTime property in Example 146 is missing a terminating Z. This erratum corrects it.

[TallTed]

It seems odd to me that a friendship is assigned a start time down to the second. Perhaps it could be bumped to the nearest hour or even the nearest day, even if sometimes the nearest minute might be known...

[csarven]

I think the resolution of startTime in the example is ok down to the second or even microsecond as long as it conforms to the range https://www.w3.org/TR/activitystreams-vocabulary/#dfn-starttime . The value generally reflects the moment that the individual triggers a button while the server minding that the client's clock may not be in sync with server's clock.

That said, a Note or Considerations section could indicate:

• clock sync concern and any changes to the value after server's processing (possible error handling here if the value is beyond an acceptable or meaningful range) - this may need to be a separate issue if not already visited
• privacy concerns with respect to the resolution