Maybe I'm being too simplistic, but given the OP's restrictions, "usually start within a 6 hour window" and "handles times over midnight", I think it's doable. If the 6 hours ended just after midnight, you would need to handle times from 18:01 - 00:01; if it started just before midnight, you would need to handle 23:59 - 5:59. For simplicity's sake, I'd make my window 18:00 - 5:59. Thus,

$n = 0;
while ( ... ) {
    $hour += 24 if( $hour < 6 );
    next if( $hour < 18 ); # ignore times outside the window
    $sum += 3600*$hour + 60*$min + $sec;
    $avg = $sum / ++$n;
}

[download]

For the $hour < 18 rule: if the time is before 6am, it's $hour would have already been adjusted to somewhere in range 24 to 29, so wouldn't trigger the <18 condition; if the time was after 6pm, it wouldn't trigger the condition; else, it will trigger the condition, and the time would be ignored.

If OP wants a narrower or wider 'accept-range', just adjust the two comparisons appropriately.

Other options would be to clamp times between 6am and noon to 05:59:59, and between noon and 6pm to 18:00:00, which will not ignore points, but manipulate them to fall within the "normal window".

I understand there are issues in the general case, but with the restrictions given, I think things are well-defined enough, and this algorithm should give a mean closer to midnight than to noon, which seems to be what the OP wants.

In reply to Re^2: Average start time handling midnight by pryrt
in thread Average start time handling midnight by chrisjej

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