How do I get a value of datetime.today() in Python that is “timezone aware”?

I am trying to subtract one date value from the value of datetime.today() to calculate how long ago something was. But it complains:

TypeError: can't subtract offset-naive and offset-aware datetimes

The value datetime.today() doesn't seem to be "timezone aware", while my other date value is. How do I get a value of datetime.today() that is timezone aware?

Right now, it's giving me the time in local time, which happens to be PST, i.e. UTC - 8 hours. Worst case, is there a way I can manually enter a timezone value into the datetime object returned by datetime.today() and set it to UTC-8?

Of course, the ideal solution would be for it to automatically know the timezone.