Pontifications

Very similar to this previous blog post: R and Lubridate: How to add daynumber starting with Firefox release date i.e. Tuesday instead of Sunday or Monday to a dataframe
Again you could also use lubridate durations, but durations aren’t accurate when you transition from month to month or year to year so use lubridate intervals instead
Here’s the code from january-august2019-plot-num-questions-release-weeks-1-4.R :

add_release_week_number <-
  function(df_release,
           yyyy,
           mm,
           dd)
  {
    START_DATE <-
      make_datetime(yyyy, mm, dd, 0, 0, 0,
                    tz = "UTC")
    return (df_release %>%
              mutate(release_week_number =
                       floor(interval(
                         START_DATE, created
                       ) / days(7)) + 1))
  }