This section specifies who is hosting, bride's parents, groom's parent's, both parents, couple hosting, etc.
There are many ways to do this but here are examples for formal/casual!
Between 8am-11:55am: “…in the morning”
Between 12pm-4:55pm: “…in the afternoon”
Between 5pm+ : “…in the evening”
Any :15, :30 – “…a quarter/half past four in the afternoon”
I suggest putting the response date at least one month before your wedding date