If you prefer to manually edit the file yourself you should first make a back up of the original /templates/base/scripts/BxBaseProfileView.php

Then open the file up and find:

	function showBlockPFBlock( $sCaption, $sContent, $bNoDB = false ) {
		$iBlockID = (int)$sContent;
		if( !isset( $this -> aPFBlocks[$iBlockID] ) or empty( $this -> aPFBlocks[$iBlockID]['Items'] ) )
			return '';
		$aItems = $this -> aPFBlocks[$iBlockID]['Items'];

		$sRet = '<table class="profile_info_block" cellspacing="0" cellpadding="1">';
		
		foreach( $aItems as $aItem ) {
			$sValue1 = $this -> oPF -> getViewableValue( $aItem, $this -> _aProfile[ $aItem['Name'] ] );
			if( !$sValue1 ) //if empty, do not draw
				continue;
			
			$sRet .= '<tr>';
			$sRet .=         '<td class="profile_info_label">' . htmlspecialchars( _t( $aItem['Caption'] ) ) . ':</td>';
			
			if( $this -> bCouple ) {
				if( in_array( $aItem['Name'], $this -> aCoupleMutualItems ) ) {
					$sRet .= '<td class="profile_info_value" colspan="2">' . $sValue1 . '</td>';
				} else {
					$sValue2 = $this -> oPF -> getViewableValue( $aItem, $this -> _aCouple[ $aItem['Name'] ] );
					
					$sRet .= '<td class="profile_info_value1">' . $sValue1 . '</td>';
					$sRet .= '<td class="profile_info_value2">' . $sValue2 . '</td>';
				}
			} else {
				$sRet .=     '<td class="profile_info_value" >' . $sValue1 . '</td>';
			}
			
			$sRet .= '</tr>';
		}
		
		$sRet .= '</table>';
		
		if ($bNoDB) {
			return $sRet;
		} else {
			echo DesignBoxContent( _t($sCaption), $sRet, 1 );
		}
	}




And replace with:

//start date of birth mod	

function showBlockPFBlock( $sCaption, $sContent, $bNoDB = false ) {
$iBlockID = (int)$sContent;
if( !isset( $this -> aPFBlocks[$iBlockID] ) or empty( $this -> aPFBlocks[$iBlockID]['Items'] ) )
return '';
$aItems = $this -> aPFBlocks[$iBlockID]['Items'];

$sRet = '<table class="profile_info_block" cellspacing="0" cellpadding="1">';

foreach( $aItems as $aItem ) {
$sValue1 = $this -> oPF -> getViewableValue( $aItem, $this -> _aProfile[ $aItem['Name'] ] );
if( !$sValue1 ) //if empty, do not draw
continue;

if($aItem['Name'] == "DateOfBirth")
{

$sRet .= '<tr>';
$sRet .= '<td class="profile_info_label">' . _t( "_Age" ) . ':</td>';

$ageValue1 = age($sValue1);
if( $this -> bCouple ) {
if( in_array( $aItem['Name'], $this -> aCoupleMutualItems ) ) {
$sRet .= '<td class="profile_info_value" colspan="2">' . $ageValue1 . '</td>';
} else {
$sValue2 = $this -> oPF -> getViewableValue( $aItem, $this -> _aCouple[ $aItem['Name'] ] );

$ageValue2 = age($sValue2);

$sRet .= '<td class="profile_info_value1">' . $ageValue1 . '</td>';
$sRet .= '<td class="profile_info_value2">' . $ageValue2 . '</td>';
}
} else {
$sRet .= '<td class="profile_info_value" >' . $ageValue1 . '</td>';
}

}else{

$sRet .= '<tr>';
$sRet .= '<td class="profile_info_label">' . htmlspecialchars( _t( $aItem['Caption'] ) ) . ':</td>';

if( $this -> bCouple ) {
if( in_array( $aItem['Name'], $this -> aCoupleMutualItems ) ) {
$sRet .= '<td class="profile_info_value" colspan="2">' . $sValue1 . '</td>';
} else {
$sValue2 = $this -> oPF -> getViewableValue( $aItem, $this -> _aCouple[ $aItem['Name'] ] );

$sRet .= '<td class="profile_info_value1">' . $sValue1 . '</td>';
$sRet .= '<td class="profile_info_value2">' . $sValue2 . '</td>';
}
} else {
$sRet .= '<td class="profile_info_value" >' . $sValue1 . '</td>';
}
}
$sRet .= '</tr>';
}

$sRet .= '</table>';

if ($bNoDB) {
return $sRet;
} else {
echo DesignBoxContent( _t($sCaption), $sRet, 1 );
}
}

//end date of birth mod


Upload the already modded file to:
/templates/base/scripts/BxBaseProfileView.php
Over-writing the original.

*In your Dolphin Admin Panel "Builders" "Fields Builder" "View Profile" Date of Birth must be in the "Active Items" for a Member. 

*If you do not have Date of Birth in the Active Items area you need to drag it up there. This mod is just changing there actual Date of Birth to Age.