To clarify, each log file is named by a number that’s the epoch time divided by 86400 (the number of seconds in a day). The epoch time counts the number of seconds since Jan 1, 1970, so that divided by 86400 gives the number of days since Jan 1, 1970. For example, the log data of Apr 20, 2015 would be stored in a file named 16545.txt.