oneThis plural form is used for numbers like: 1
Every %1$d day
otherThis plural form is used for numbers like: everything else
Every %1$d days
Every %1$d day
Every %1$d days
Cada %1$d día
Cada %1$d días
Every %1$d day
Every %1$d days
Cada %1$d día
Cada %1$d días
%1$d - number