Grandpa was born on February 29, 1916. How many birth anniversaries did he pass by New Year's Day in 1996?
爷爷出生于1916年2月29日，到1996年元旦，他过了多少个出生纪念日．
<gadget id="calculator">1_996 - 1_916</gadget>
<output>80</output>

<gadget id="calculator">80 / 4</gadget>
<output>20</output>

<result>20</result>