It looks like python, so the semi-colons are unnecessary.
If you want to rid yourself of datetime for whatever reason, implement it as a list, returning name_of_day[x], so that you can start the week on a Sunday(=0) easily if you want to.
Python ships with a standard datetime class which is powerful enough to represent time, and there is a ubiquitous module, dateutil, which extends it to do nearly anything people need to do with dates regularly.
Additionally, one would normally use an array of names and index it: