> df$date_put_on_list <- as.POSIXct(df$date_put_on_list, format = "%m/%d/%Y", tz = "EST")

It's a cool blog post but that code isn't near readable to me. Long lines in a tiny rectangle hidden behind horizontal scroll don't make it any easier. It looks like a box of arbitrary characters stuffed into as little space as possible.

Although the raw link is a little easier on the eyes:

https://gist.githubusercontent.com/statwonk/9448932/raw/84b9...

Whoever named that method POSIXct needs to like leave the job of naming things to other people maybe.