Solely use datetime objects for timing

Also added some comments, and a different thing to write to logs when
commands are run. Oh and I changed a p to a u since it seems to contain a user object so u seemed to make more sense.
Could use a list comprehension here.  Something like:
```python
header = "User\t\tLast login \t\tLast logout"]
fmt = "{0}\t\t{1[lastlogin]:%d/%m/%y %H:%M}\t\t{1[lastlogout]:%d/%m/%y %H:%M}"
content = [fmt.format(user_key, user_val) for user_key, user_val in userlogininfo.iteritems()]
msg_list = header + fmt
```
mayhaps? (I haven't tested this extensively to make sure it works, don't sue me)