Function and verb to convert Excel-generated date integers into seconds since the epoch

[pjfarleyiii]

A function and a main verb to convert Excel-generated date integers to "seconds since the [unix] epoch" for input to other miller date/time functions.

I ran into this issue while saving an Excel worksheet as a csv file with "Show Formulas" turned on so that cell formulas would be saved as strings rather than as the value generated by the formula, but the other result was that the Date column was saved as the Excel integer date value, not as a formatted date.

Excel dates are integers representing "days since 1900-01-01", so Excel generates an integer value 41647 to represent the date 2014-01-08, and the integer value 25569 to represent the date 1970-01-01.

I wrote a simple DSL to do the conversion manually, where field $Date is an Excel-generated integer date, but it would be nice if the conversion was a builtin function ("exceldate()" perhaps?):

$Date = sec2gmtdate(($Date - 25569) * 86400)