LastWriteTime

LastWriteTime is a metadata timestamp associated with a file or directory that records the time of the most recent write operation. It serves as an indicator of when the content was last modified and is distinct from CreationTime (when the item was created) and LastAccessTime (when it was last read). On many file systems, LastWriteTime is the modification time, or mtime, used by tools and applications to determine freshness or to decide whether a file needs to be reprocessed.

In programming environments, LastWriteTime is commonly exposed as a property of file information objects. For example, in Windows and .NET, FileInfo and DirectoryInfo expose LastWriteTime, and there is a corresponding LastWriteTimeUtc for the universal time representation. Reading this property yields the local time, while the UTC variant provides a standard reference. In shells and scripting contexts, such as PowerShell, LastWriteTime is typically available as a property of file objects returned by commands like directory listings.

Cross-platform considerations are important. Windows stores file times with a high-resolution internal representation, while Unix-like systems represent modification times (mtime) with their own granularity, which may vary by filesystem. When moving or copying files between systems, LastWriteTime may be preserved, reset, or require explicit handling, depending on the tool.

Common uses include sorting files by modification date, filtering recently changed items, and diagnosing updates or backups. Users should be mindful of time zone handling when interpreting LastWriteTime, as local time and UTC representations may differ, and of potential granularity limitations on certain filesystems.