index=test | addinfo | eval Tdate=strptime(Transaction_date,"%Y-%m-%d %H:%M:%S.%1N") | where Tdate >= info_min_time AND Tdate <= info_max_time | ...
Epoch time is the Unix timestamp standard. It's the number of seconds since 1 Jan 1970 (IIRC). Converting dates to epoch (integer) form makes it vastly easier to compare and manipulate them.
If this reply helps you, Karma would be appreciated.