# DateSystem ```csharp public enum DateSystem ``` Namespace `SharpCell` · package `SharpCell` The workbook's date system: which day serial number 0 or 1 stands for. ## Values | Name | Value | Description | |---|---|---| | `Date1900` | 0 | Serial 1 is 1900-01-01 and the non-existent 1900-02-29 is serial 60, as in Excel for Windows. | | `Date1904` | 1 | Serial 0 is 1904-01-01, as in old Excel for Mac. |