Can't disable periodic file rotation

Hi,

In README.md, I found following description about log-file rotation.

> To disable rotation set the size to 0 and the date to "".

I tried the above settings, but log file was rotated in midnight.
(In lager_file_backend.erl, if 'date' value is "", the default value "$D0" will be used instead.)

I want to control file rotation via an external program (not lager).

Is there any schedule which corrects this point ?