When is it appropriate to submit a resignation letter at work?

Generally, it is better to submit your resignation letter one hour before work in the afternoon. First, it will not affect the working mood of the leaders for one day. Second, the leader will think that you didn't delay your work because you left your job today. Third, it will give leaders a time to think after work, which is the safest and a good choice for both sides.

I hope my answer will help you and be adopted by you.