To convert the time from 12 hour clock format to 24 hour clock format, we need to add 12 hours to the given time followed by pm.
Here time is 8:30 at night, so 8 hours 30 minutes + 12 hours = 20 hours 30 minutes = 20:30 pm.
So, the time written on railway ticket is 20:30 pm.
The correct answer is option C - 20:30 pm.