I am looking for a timer that can trip the shutter at a specified delay and then open the shutter for a specified amount of time. Ideally both the trip shutter delay and open shutter timer could be programmed anywhere from seconds to hours or even a programable time of the day (eg trip the shutter at 2100 on the 10th of January 2019 and open the shutter for 3 hrs, or close the shutter at 0000 on 11th of January 2019).

Do such devices exist?

I also noticed there were some more basic mechanical timers that would be great to get your opinions on? While they seem not to be that flexible, they might at least serve the purpose of self portrait shutter delay and potentially some longer timed exposures?