--- a/toolkit/components/telemetry/docs/core-ping.rst
+++ b/toolkit/components/telemetry/docs/core-ping.rst
@@ -31,16 +31,18 @@ Structure::
       "seq": <positive integer>, // running ping counter, e.g. 3
       "locale": <string>, // application locale, e.g. "en-US"
       "os": <string>, // OS name.
       "osversion": <string>, // OS version.
       "device": <string>, // Build.MANUFACTURER + " - " + Build.MODEL
                           // where manufacturer is truncated to 12 characters
                           // & model is truncated to 19 characters
       "arch": <string>, // e.g. "arm", "x86"
+      "profileDate": <pos integer>, // Profile creation date in days since
+                                    // UNIX epoch.
 
       "experiments": [<string>, …], // Optional, array of identifiers
                                     // for the active experiments
     }
 
 The ``device`` field is filled in with information specified by the hardware
 manufacturer. As such, it could be excessively long and use excessive amounts
 of limited user data. To avoid this, we limit the length of the field. We're