is_ISO8601.Rd
checking YYYYY-mm-dd format of date variables
is_ISO8601(date_col)
character vector, vector containing dates to check
boolean, when TRUE all values of date_col are in the required format, when FALSE at least one is not in required format
if (FALSE) {
is_ISO8601(c("2023-04-01", "2022-12-31"))
}