To ensure that older workbooks are calculated correctly, Excel behaves differently when you first open an old workbook than when you open a workbook created in the current version.
When you open a workbook created in the current version, Excel recalculates only the formulas that depend on cells that have changed.
Because complete recalculation can take longer than partial recalculation, opening a workbook that was not previously saved in the current Excel version can take longer than usual. Once you save the workbook in the current version, it will open faster.
When you open a workbook created in the current version, Excel recalculates only the formulas that depend on cells that have changed.
When you use open a workbook that was created in a earlier version of Excel, all of the formulas in the workbook — those that depend on cells that have changed and those that do not — are recalculated. This ensures that the workbook is fully optimized for the current Excel version.