Can someone tell me how to delete 3 months of Chat. Every time I open MIRC it picks up where it left off with a line between chats

You can turn logging and/or the 'reloading' of logs into windows in mIRC Options -> IRC -> Logging.

You can delete log files in Tools -> Log Files

By default, there is no feature where you can get mIRC to delete all logs before x days ago from today.

There is a feature, though, where you can set the size of the log files. Suppose you want log files to not exceed 5 megabytes. Since the feature is represented by kilobytes, you'll have to convert. Etc. But no, no date or time reference.

-Neal.