Refer to the Getting started with Python guide, the date can be relative (e.g. -10D, -2Y, 3M) or absolute (e.g. 2018-11-09) date format. Moreover, it can be the following values:
LATESTDATE BDATE DEFAULTDATE MTE QTE SQDATE SWDATE SYDATE TODAY WKE YRE
If this doesn't answer your question, please explain more about the question. For example, please share the code that you are using or the data types that you want to get.