Converting Excel Dates to UNIX Timestamps
A previous article showed how to convert a UNIX Timestamp to an Excel Date. It’s also possible to do the reverse- convert an Excel Date value to a UNIX formatted Timestamp.
Where cell A2 contains an Excel Date time this formula produces a UNIX timestamp.
In the example the Date cell (column A) is formatted with the custom format
dd/mm/yy hh:mm:ss and the Timestamp cell (column B) is formatted as a Number to 0 decimal places.