From Quake Wiki
Note: This QC extension was originally implemented by mvdsv, however its original version was not queryable, and its builtin number conflicted with existing QSG builtins. The FTE version of the extension is otherwise functionally identical.
void() calltimeofday = #231; noref void(float secs, float mins, float hour, float day, float mon, float year, string strvalue) timeofday;
When this builtin is called, the engine will query the the operating system's local time and then directly call the QC's 'timeofday' function (thereby providing a workaround for builtins being unable to return more than 1 arg, although will generally still result in global abuse, but hopefully less than there otherwise would be).
For a more versatile alternative, look for DP_QC_STRFTIME.