Thanks for working on this. It's a good start but there's some things to fix up.

Module names should be alphabetized, and the imports for datetime and timedelta should go on the same line (from datetime impor datetime, timedelta).

Two blank lines before the class definition.

Could you briefly document the BZRTool, explain its purpose?

The print statements should go away.

Excess trailing whitespace. Here and elsewhere in the file.

What's the difference between rev and revision? Could you add a comment explaining this?

These look indented too far.

Also, I'm not wild about referencing the values by position. Can you instead split the line and check the parts for "revno:" and "timestamp:" and grab the value that way?

There's probably a better way to structure this. There's a lot of magic numbers for positions in here. What's this supposed to do?

Mix of spaces and tabs for the leading whitespace. It should be spaces only.

This is my second attempt.

Unfortunately this system did not let me update tbe diff twice, and thus these extra spaces are still here.

I went ahead and made various style changes and committed this as r1300.  Thanks!

This should be up in the standard-library group, alphabetically.