The HTTP Last-Modified response header indicates the date and time that the resource was last modified.
The Last-Modified response header is similar to the HTTP Date response header, except it indicates the date and time that the server believes the resource was last modified rather than generated. This HTTP header can be used as a condition, or validator in a conditional request. For example, HTTP requests that use the HTTP If-Modified-Since or If-Unmodified-Since headers will refer to the last modified date.
The directives are day-name, day, month, year, hour, minute, second, and GMT.
For a complete description of the directives, please refer to the HTTP Date header.
In this example, the resource was last modified on June 1st, 2022, at 8 am GMT.
Last-modified: Wed, 01 Jun 2022 08:00:00 GMT
The Last-Modified response header indicates when the resource was last modified.