Test that Excel number formats are date formats

is_date_format() tests whether an Excel number format string would a resolve to a date in Excel. For example, the number format string "yyyy-mm-dd" would resolve to a date, whereas the string "0.0\\%" would not.

This is useful if a cell formula contains a number formatting string (e.g. TEXT(45678,"yyyy")), and you need to know that the constant 45678 is a date in order to recover it at full resolution (rather than parsing the character output "2025" as a year).

It is used internally to convert the value of a cell to the correct data type.

Usage

is_date_format(x)

Arguments

x

character vector of number format strings

Examples

is_date_format(c("yyyy-mm-dd", "0.0%", "h:m:s", "£#,##0;[Red]-£#,##0"))
#> [1]  TRUE FALSE  TRUE FALSE