If you are writing a bullying report for HR but you only have a vague
idea of when the incident happened e.g. Early in March what do you
You say it happened "early in March". (You really shouldn't just make up a date)
Do you say that you don't know when?
You could, but since you do know it was early in March, you can do better.
Or explain why you didn't write it down?
I mean you don't usually write down stuff that someone walks up to you
and out of the blue says.
You probably don't need to explain why you didn't do something unless you are asked why.
You really need to consult your lawyer first if you are trying to build a case. Otherwise, when you aren't sure what to write - ask HR how specific your answers on their report need to be.