RS
http://logback.qos.ch/manual/appenders.html#tbrpFileNamePattern
Multiple %d specifiers
It is possible to specify multiple %d specifiers but only one of which can be primary, i.e. used to infer the rollover period. All other tokens must be marked as auxiliary by passing the 'aux' parameter (see examples below).
Multiple %d specifiers allow you to organize archive files in a folder structure different than that of the roll-over period. For example, the file name pattern shown below organizes log folders by year and month but roll-over log files every day at midnight.
/var/log/%d{yyyy/MM, aux}/myapplication.%d{yyyy-MM-dd}.log