If you are starting from a fresh sites, you'll most likely never experience issues explained here
Failed to parse time string
This is a very common error, specially for the sites which have old database (several years old sites) or those with a lot of dirty data
It looks like the error does not tell us anything special, but if you take a closer look, the error actually said that is failing to parse date string 1987-34-58 23:59:59 which is true, because 1987-34-58 23:59:59 can never be an actual date
In this case, 1987 is the year, 34 is the month and 54 is the day. Obviously, the date here is wrong.
It can also happen that you have completely date unrelated value like random string of characters, solution will however, be the same.
First, navigate to your database. You will most likely use phpMyAdmin as a common software to manage your database
Once database have been selected, navigate to Search tab
Insert the word you want to search for. In our case, it would be 1987-34-58 23:59:59'
Select to find exact phrase - This is particularly important as 1987 is a valid year and it could find more records if we don't set this option
Select All tables to be searched and click on Go button
You should see similar result like on the picture bellow
You can now either delete the record, or browse it further. Lets just click on Delete. We will leave up to you if you want to browse it further.
Now refresh your JomSocial dashboard. If error is gone, good, if other error is thrown (most likely on a large and dirty databases) just repeat the same process.