Detects Date and/or POSIXct column(s) in a data.frame.
Examples
has_date(data.frame(date = Sys.Date()))
#> [1] "date"
has_date(data.frame(date = Sys.Date(), update = Sys.Date()), single = FALSE)
#> [1] "date" "update"
has_date(data.frame(date = Sys.Date(), update = Sys.Date()), single = TRUE)
#> [1] "date"