Will viral or bacterial pneumonia cure itself depending on time?

Maybe but it depends: I know you want a more definitive answer but my crystal ball is in the shop being repaired. Is it possible to get over an pneumonia (and for that matter, any other infection) w/o taking antibiotics? Sure! but unless the infection is mild and you're super healthy, the odds aren't in your favor. While we can't treat viral infections (unlike bacterial ones), we can provide respiratory, etc support.

Maybe: Bacterial pneumonia should be treated with antibiotics, it is possible that the infection could spontaneously resolve without treatment as it did sometimes in the pre antibiotic era. This is not something one should risk as bacterial pneumonia can be severe even life threatening and is best treated with antibiotics. There are no antibiotics for viral pneumonia ( except flu) . Both need support.