Practical diagnosis

When dates shift by 1,462 days

Reviewed 8 October 2026 · Synthetic examples

A cluster of dates roughly four years out can indicate a date-system mismatch. It is a diagnostic clue, not a reason to add 1,462 to every value. First establish one known calendar date and inspect the source and destination workbook settings.

One date, different numbers Excel supports 1900 and 1904 date systems. For January 1, 2026, the numeric serial is 46023 in the 1900 system and 44561 in the 1904 system. The difference is 1462. Google Sheets counts days from December 30, 1899 and uses 46023 for this modern date. These sample counts are independently calculated calendar arithmetic, under the documented epochs.

For an explicitly identified raw 1904 serial, 44561 + 1462 = 46023 translates that date into the modern 1900-system serial. Going the other direction requires subtraction: 46023 - 1462 = 44561. Keep the original value and label the assumed system beside the converted value. Never infer the system from a five-digit number alone.

Excel’s documentation locates the Windows setting under File > Options > Advanced > When calculating this workbook. On Mac it describes Preferences > Calculation. Check the actual workbook, not merely whether it came from a Mac: modern Mac workbooks need not use the older system.

Do not apply the correction twice A workbook transfer can already convert dates. Before arithmetic, compare several known source and destination calendar dates and inspect the values. If they already agree, leave them alone. Changing a whole workbook’s date-system setting is also broader than repairing a specific imported column; experiment only on a copy and review dependent formulas and charts.

The historical exception Excel retains a historical assumption that 1900 was a leap year. Sheets explicitly treats it as a common year. Consequently, their early serials are not interchangeable: January 1, 1900 is Excel 1900-system serial 1 and Sheets serial 2. Excel’s serial 60 represents its fictitious February 29, 1900; Sheets serial 60 is February 28. At March 1, both use 61.

Do not build a universal converter by blindly adding a fixed epoch to every Excel serial. A converter handling historical material must name the source system and explicitly handle the fictitious day. For ordinary modern records, a known-date spot check is still essential. An unexplained one-day discrepancy is a different investigation from the 1,462-day mismatch and should not receive the same repair.