Not an S3 method, which might have conflicted with stats::confint.
confint_numeric(object, level = 0.95, B = 0)the vector [conf_inf, conf_sup]
confint_numeric(iris$Sepal.Length)
#> 2.5 % 97.5 %
#> 5.710818 5.975849
confint_numeric(mtcars2$hp_date)
#> 2.5 % 97.5 %
#> "2010-05-03" "2010-06-20"
confint_numeric(mtcars2$hp_date, level=0.99)
#> 0.5 % 99.5 %
#> "2010-04-26" "2010-06-27"