index.cgiの上の方にある下記の部分の2行目と3行目の間に
$year = $year + 1900;
を追加してください。

■修正前
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($sec,$min,$hour,$mday,$mon,$year,$wno) = localtime(time);
@wdays = ('日','月','火','水','木','金','土');
$year = substr($year,2,2);
$niti = sprintf("%02d/%02d/%02d(%s) %02d:%02d:%02d",$year,$mon+1,$mday,$wdays[$wno],$hour,$min,$sec);
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■修正後
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($sec,$min,$hour,$mday,$mon,$year,$wno) = localtime(time);
@wdays = ('日','月','火','水','木','金','土');
$year = $year + 1900;
$year = substr($year,2,2);
$niti = sprintf("%02d/%02d/%02d(%s) %02d:%02d:%02d",$year,$mon+1,$mday,$wdays[$wno],$hour,$min,$sec);
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