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
Каждые %1$d день
Каждые %1$d дней
Каждые %1$d дней
Every %1$d day
Every %1$d days
Every %1$d day
Every %1$d days
Каждые %1$d день
Каждые %1$d дней
Каждые %1$d дней
%1$d - number