wtmp file

sorry for being a noob, i am trying to find which user accessed the server at what time and there ip address at first i used who command but the output didn't contain the ip address then i used the last command which provided me with the ip of the users but when i searched i searched and found that both commands use to retrieve the data from a file called wtmp.
- does both use the same file ?
- i found that the file contains only record for the last day how can i increase the time the this file hold the data ?
- is there a patch to export the data another file each day ?