Student or Learner
I have been admitted to a hospital in january
I was admitted to a hospital in january or
I have been admitted to a hospital last january
Which one is correct
When you refer to a specific time in the past, use simple past, not present perfect.
Remember to capitalize months.
I was admitted to the hospital [last] January.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.