history: For my anniversary at my job, all my coworkers threw me a party. I had no idea until I walked into the office at lunch. Last month for my 20th anniversary at my job_comma_ my coworkers threw me a party. That is so nice of them!
current: I had no idea till I walked into the office with my boss on lunch. I was completely shocked.
next: I am so happy for you! Congrats!