> For the complete documentation index, see [llms.txt](https://developer.prodege.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.prodege.com/surveys-feed/api-reference/authentication/request-expiration.md).

# Request Expiration

Each request to Prodege APIs must be timestamped. In some cases, the request timestamp will be used to identify old and expired API requests. The “request\_date” parameter will hold the request timestamp and it will also be used to generate the request signature.

The value for the “request\_date” parameter is to be calculated in this manner:

<mark style="color:purple;">request\_date =</mark> <mark style="color:purple;"></mark>*<mark style="color:purple;">client\_time</mark>* <mark style="color:purple;"></mark><mark style="color:purple;">+</mark> <mark style="color:purple;"></mark>*<mark style="color:purple;">request\_time\_offset</mark>*

where *<mark style="color:purple;">client\_time</mark>* is your time in milliseconds, and *<mark style="color:purple;">request\_time\_offset</mark>* is the amount of time difference (in milliseconds) between your time and the ProdegeMR Server’s time. *<mark style="color:purple;">request\_time\_offset</mark>* can be determined by issuing the Lookup Request Time Offset API Call.