The first version of Excel shipped in 1985 for the Apple Macintosh. The first Windows version (Excel 2.0) arrived in 1987.

1900 was not a leap year, but Excel treats it as one. The bug was copied on purpose from Lotus 1-2-3 so that spreadsheets moved between the two programs would keep the same date serial numbers. It is still there today for compatibility.

Since Excel 2007 every sheet has 1,048,576 rows and 16,384 columns (A to XFD). Multiply them and you get just over 17 billion cells — per sheet. Your laptop runs out of memory long before you run out of cells.