=CONCATENATE(INT((A1-7385)/365.25)+1299,"/",MOD(IF(INT(MOD((A1-7385)*100,36525)/100)<186,INT(INT(MOD((A1-7385)*100,36525)/100)/31),IF(MOD(INT((A1-7385)/365.25),4)=0,INT((INT(MOD((A1-7385)*100,36525)/100)-186)/30)+6,IF(INT(MOD((A1-7385)*100,36525)/100)<336,INT((INT(MOD((A1-7385)*100,36525)/100)-186)/30)+6,INT((INT(MOD((A1-7385)*100,36525)/100)-336)/29)+11))),12)+1,"/",IF(INT(MOD((A1-7385)*100,36525)/100)<186,MOD(INT(MOD((A1-7385)*100,36525)/100),31)+1,IF(MOD(INT((A1-7385)/365.25),4)=0,MOD(INT(MOD((A1-7385)*100,36525)/100)-186,30)+1,IF(INT(MOD((A1-7385)*100,36525)/100)<336,MOD(INT(MOD((A1-7385)*100,36525)/100)-186,30)+1,MOD(INT(MOD((A1-7385)*100,36525)/100)-336,29)+1))))