Access Android log files for specific periods on android 7
Android does not store the output of logcat in flash memory. Instead logcat uses a ring buffer in RAM of usually 64KB up to 4MB (depends on what is configured). RAM is much faster than flash memory and also flash may fail earlier if constantly logmessages are written onto it.

A ringbuffer means that if the buffer is full the oldest entry will be overwritten by a new entry. Therefore logcat usually only contains the last minutes or hours. And only log messages after the last reboot as the logcat buffer is not saved on shutdown and the RAM memory is also lost on reboot.

Therefore there are no old log messages you can access.