Push up extra type docs

R/type.R

@@ -5,7 +5,17 @@
 #' 'xportr.character_types' option is used to explicitly collapse the class of a
 #' column to character using `as.character`. Similarly, 'xportr.numeric_types'
 #' will collapse a column to a numeric type. If no type is passed for a
-#' variable, it is assumed to be numeric and coerced with `as.numeric`.
+#' variable and it isn't identifed as a timing variable, it is assumed to be numeric and coerced with `as.numeric`.
+#'
+#' Certain care should be taken when using timing variables. R serializes dates
+#' based on a reference date of 01/01/1970 where XPT uses 01/01/1960. This can
+#' result in dates being 10 years off when outputting from R to XPT if you're
+#' using a date class. For this reason, `xportr` will try to determine what
+#' should happen with variables that appear to be used to denote time.
+#'
+#' For variables that end in DT, DTM, or, TM, if they are not explicitly noted
+#' in 'xportr.numeric_types' or 'xportr.character_types', they are coerced to
+#' numeric results.
 #'
 #' @inheritParams xportr_length
 #'