R转换具有不同格式的日期列表

Question

因此，我有一些日期列表，由于以下原因，我无法完全将其视为日期：

Error in charToDate(x) : character string is not in a standard unambiguous format

数据以字符向量形式输入，并在最后一行代码之后转换为未知数据。我最终希望在这些日期之前对数据进行排序，但是由于这些数据被视为字符向量，因此无法正确排列。

样本数据： http://www.fast-files.com/getfile.aspx?file=191192 http://www.fast-files.com/getfile.aspx?file=191193

library("xlsx")
library("readxl")
library("dplyr")
library("data.table")
library("tidyverse")
library("lubridate")
library("zoo")
library("stringr")
A <- read_csv("A.csv")
B <- read_csv("B.csv")
C<- rbind(A,B)
C[C=="/  /"]<-NA
as.Date(C$`ROLL OUT SHIP DATE`)
format <- guess_formats(c(C$`ROLL OUT SHIP DATE`), c("mdY", "BdY", "Bdy", "bdY", "bdy", "mdy", "dby"))
C$`ROLL OUT SHIP DATE` <-as.Date(strptime(C$`ROLL OUT SHIP DATE`, format))

a.csv数据：

"Due Date","ROLL OUT SHIP DATE","Vendor Ship Date"
"04/01/2019","/  /","02/25/2019"
"06/06/2019","/  /","04/30/2019"
"04/01/2019","/  /","02/25/2019"
"03/09/2019","/  /","/  /"
"03/09/2019","/  /","/  /"
"03/09/2019","/  /","/  /"
"05/01/2019","/  /","03/25/2019"
"05/10/2019","/  /","04/03/2019"
"05/01/2019","/  /","03/25/2019"
"05/10/2019","04/01/2019","04/03/2019"
"04/24/2019","05/01/2019","03/25/2019"
"03/09/2019","/  /","/  /"
"/  /","/  /","/  /"

b.csv：

"Due Date","ROLL OUT SHIP DATE","Vendor Ship Date"
"04/06/2019","04/07/2019","03/13/2019"
"04/21/2019","04/07/2019","04/03/2019"
"03/30/2019","02/18/2019","03/04/2019"
"03/30/2019","/  /","03/04/2019"
"02/10/2019","/  /","/  /"
"04/05/2019","/  /","02/25/2019"
"06/14/2019","/  /","05/01/2019"
"03/08/2019","/  /","01/21/2019"
"03/08/2019","/  /","01/21/2019"
"03/22/2019","/  /","02/04/2019"
"03/31/2019","04/08/2019","02/25/2019"
"08/03/2019","/  /","06/20/2019"
"08/03/2019","/  /","06/20/2019"
"03/04/2019","/  /","/  /"
"07/30/2019","/  /","06/16/2019"
"07/30/2019","/  /","06/23/2019"
"03/25/2019","/  /","/  /"
"03/29/2019","/  /","/  /"
"03/29/2019","/  /","/  /"
"03/29/2019","/  /","/  /"
"03/29/2019","/  /","/  /"
"03/31/2019","/  /","02/25/2019"
"05/14/2019","/  /","04/01/2019"
"06/17/2019","/  /","05/05/2019"
"03/07/2019","/  /","01/20/2019"
"06/07/2019","/  /","05/01/2019"
"03/16/2019","04/08/2019","01/28/2019"
"03/16/2019","/  /","02/05/2019"
"04/11/2019","/  /","03/05/2019"
"05/15/2019","/  /","04/08/2019"
"06/09/2019","/  /","05/03/2019"
"05/08/2019","/  /","04/01/2019"
"06/12/2019","/  /","04/29/2019"
"/  /","/  /","/  /"
"/  /","/  /","/  /"