Remove old data over 1 year old

I have had my IotaWatt for over 4 years and it has been working perfectly until recently when it would just freeze I changed the firmware version and this seemed to fix it for a few more months and now again it’s doing the same thing so I have now switched out the SD card and everything seems to be working again but my log file is over 1.6gb and wanted only to keep the last 12 months of data is this possible?

I’d like to be able to do this too please.