Skip to main content

IfModifiedSince

property IfModifiedSince: TDateTime read;

Example​

procedure ScriptEvent(var Value: variant);
begin
  if (Request <> nil) and (Request.IfModifiedSince >= 0) then
    Value := Request.IfModifiedSince
  else
    Value := 0;
end;

Usage​

IfModifiedSince parses the first If-Modified-Since value, returning -1 when absent and leaving conditional-response decisions to the flow.

Additional Technical Info​

IfModifiedSince selects the first raw If-Modified-Since value and uses WebBroker's date parser. Empty returns -1; invalid nonempty syntax can raise. Standard weekday-leading HTTP-date text becomes a timezone-free TDateTime representing UTC, while limited numeric-leading legacy formats take the older non-timezone-converting path.

Reading the property does not evaluate a resource timestamp, set status 304, suppress content or configure caching. HTTP defines this as a conditional request validator normally evaluated only when the selected representation has a known modification date, and more specific validators can take precedence.

Do not use a caller-supplied date for access control or as proof of data version. If implementing conditional retrieval, distinguish the sentinel, compare at HTTP-date precision with the server-controlled representation timestamp, apply method/precondition precedence, and set the response deliberately. Invalid fields should become a controlled result rather than an unhandled script exception.

Test Request for nil. This property has no automatic relationship to Velox Configuration/Map modification dates.

External references

Created 2026-07-15