AtkDateAttribute
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Note that ATK uses an internal format for storing data in attributes. The date attribute stores the date value in an array with the 'year', 'month' and 'day' elements.
To convert a string value to the internal representation, e.g. when setting an initial value, use the attribute method parseStringValue.
$attr = $this->getAttribute("orderdate");
$record["orderdate"] = $attr->parseStringValue("2010-01-09");