// output date with current year set at first day of year
$currentYearStartDate = $this->DateTime->setDate(
$this->DateTime->format('Y'), 1, 1
)->format('Y-m-d');
// output date with previous year and current day
$previousYearEndDate = $this->DateTime->setDate(
$this->DateTime->format('Y'), 1, 1
)->format('Y-m-d');
// output date with previous year set at first day of year
$previousYearStartDate = $this->DateTime->sub(
new DateInterval('P12M')
)->format('Y-m-d');