This is a difficult but valid issue. I'm still experimenting with it in my own RP but I think I'm starting to settle down on something somewhat similar to what you are doing. But not as extensively. Basically GM goes and posts current time (something general like "Day 4, Daytime") and everything that comes before (like if you wanna write about your character having breakfast) you put it in a hider on top of your post and indicate when that takes place.

It helps significantly if your players all have some sort of private messaging system figured out. Saves tremendous amount of time and chronological screw ups. Like writing out a conversation in a PM and then someone posting it for both players.