IF(DATEDIF(a1,b1,"Y")>3,DATEDIF(a1,b1,"Y")+"岁",DATEDIF(a1,b1,"Y")+"岁"+MOD(DATEDIF(a1,b1,"M"),12)+"月")
B1自己替换成当前日期
IF(DATEDIF(a1,TODAY(),"Y")>3,DATEDIF(a1,TODAY(),"Y")+"岁",DATEDIF(a1,TODAY(),"Y")+"岁"+MOD(DATEDIF(a1,TODAY(),"M"),12)+"月")
前面的有点不严谨 应该这样
IF(DATEDIF(a1,TODAY(),"Y")>3,DATEDIF(a1,TODAY(),"Y")+"年",TRUNC(DATEDIF(a1,TODAY(),"M")/12)+"年"+MOD(DATEDIF(a1,TODAY(),"M"),12)+"月")