When you create a new entry from an existing file by calling the xref:System.IO.Compression.ZipFileExtensions.CreateEntryFromFile%2A method, the xref:System.IO.Compression.ZipArchiveEntry.LastWriteTime%2A property for the entry is automatically set to the last time the file was modified. When you create a new entry programmatically by calling the xref:System.IO.Compression.ZipArchive.CreateEntry%2A method, the xref:System.IO.Compression.ZipArchiveEntry.LastWriteTime%2A property for the entry is automatically set to the time of execution. If you modify the entry, you must explicitly set the xref:System.IO.Compression.ZipArchiveEntry.LastWriteTime%2A property if you want the value to reflect the time of the latest change.
When you set this property, the xref:System.DateTimeOffset value is converted to a timestamp format that is specific to zip archives. This format supports a resolution of two seconds. The earliest permitted value is 1980 January 1 0:00:00 (midnight). The latest permitted value is 2107 December 31 23:59:58 (one second before midnight). If the value for the last write time is not valid, the property returns a default value of 1980 January 1 0:00:00 (midnight).
The following example shows how to open an entry in a zip archive, modify it, and set the xref:System.IO.Compression.ZipArchiveEntry.LastWriteTime%2A property to the current time.
:::code language="csharp" source="/snippets/csharp/System.IO.Compression/ZipArchive/GetEntry/program2.cs" id="Snippet2":::
:::code language="vb" source="/snippets/visualbasic/System.IO.Compression/ZipArchive/GetEntry/program2.vb" id="Snippet2":::