These docs are for an old release.
Info on upgrading to version 2/3
weekNumbers 1.6
Determines if week numbers should be displayed on the calendar.
Boolean, default: false
If set to true, week numbers will be displayed in a separate left column in the month/basic views as well as at the top-left corner of the agenda views.
By defaut, FullCalendar will display the ISO8601 week number. To display other types of week numbers, see weekNumberCalculation.